diff --git a/PSCollectionView.h b/PSCollectionView.h
index 0bbe669..30275ea 100644
--- a/PSCollectionView.h
+++ b/PSCollectionView.h
@@ -31,20 +31,24 @@
 
 #pragma mark - Public Properties
 
-@property (nonatomic, retain) UIView *headerView;
-@property (nonatomic, retain) UIView *footerView;
-@property (nonatomic, retain) UIView *emptyView;
-@property (nonatomic, retain) UIView *loadingView;
+@property (nonatomic, strong) UIView *headerView;
+@property (nonatomic, strong) UIView *footerView;
+@property (nonatomic, strong) UIView *emptyView;
+@property (nonatomic, strong) UIView *loadingView;
 
+@property (nonatomic, assign, readwrite) CGFloat margin;
 @property (nonatomic, assign, readonly) CGFloat colWidth;
 @property (nonatomic, assign, readonly) NSInteger numCols;
 @property (nonatomic, assign) NSInteger numColsLandscape;
 @property (nonatomic, assign) NSInteger numColsPortrait;
-@property (nonatomic, assign) id <PSCollectionViewDelegate> collectionViewDelegate;
-@property (nonatomic, assign) id <PSCollectionViewDataSource> collectionViewDataSource;
+@property (nonatomic, assign) BOOL animateLayoutChanges;
+@property (nonatomic, weak) id <PSCollectionViewDelegate> collectionViewDelegate;
+@property (nonatomic, weak) id <PSCollectionViewDataSource> collectionViewDataSource;
 
 #pragma mark - Public Methods
 
+- (void)invalidateLayout;
+
 /**
  Reloads the collection view
  This is similar to UITableView reloadData)
@@ -55,7 +59,12 @@
  Dequeues a reusable view that was previously initialized
  This is similar to UITableView dequeueReusableCellWithIdentifier
  */
-- (UIView *)dequeueReusableView;
+- (PSCollectionViewCell *)dequeueReusableViewWithIdentifier:(NSString *)reuseIdentifier;
+
+- (void)insertItemAtIndexPath:(NSIndexPath *)indexPath;
+- (void)removeItemAtIndexPath:(NSIndexPath *)indexPath;
+
+- (void)performBatchUpdates:(void (^)(void))updates completion:(void (^)(void))completion;
 
 @end
 
@@ -64,7 +73,7 @@
 @protocol PSCollectionViewDelegate <NSObject>
 
 @optional
-- (void)collectionView:(PSCollectionView *)collectionView didSelectView:(PSCollectionViewCell *)view atIndex:(NSInteger)index;
+- (void)collectionView:(PSCollectionView *)collectionView didSelectView:(PSCollectionViewCell *)view atIndexPath:(NSIndexPath *)indexPath;
 
 @end
 
@@ -73,8 +82,12 @@
 @protocol PSCollectionViewDataSource <NSObject>
 
 @required
-- (NSInteger)numberOfViewsInCollectionView:(PSCollectionView *)collectionView;
-- (PSCollectionViewCell *)collectionView:(PSCollectionView *)collectionView viewAtIndex:(NSInteger)index;
-- (CGFloat)heightForViewAtIndex:(NSInteger)index;
+- (NSUInteger)numberOfSectionsInCollectionView:(PSCollectionView *)collectionView;
+- (NSUInteger)collectionView:(PSCollectionView *)collectionView numberOfViewsInSection:(NSUInteger)section;
+- (PSCollectionViewCell *)collectionView:(PSCollectionView *)collectionView viewAtIndexPath:(NSIndexPath *)indexPath;
+- (CGFloat)collectionView:(PSCollectionView *)collectionView heightForViewAtIndexPath:(NSIndexPath *)indexPath;
+
+@optional
+- (UIView *)collectionView:(PSCollectionView *)collectionView sectionHeaderForSection:(NSUInteger)section;
 
 @end
diff --git a/PSCollectionView.m b/PSCollectionView.m
index 768c76c..470cf55 100644
--- a/PSCollectionView.m
+++ b/PSCollectionView.m
@@ -23,27 +23,25 @@
 
 #import "PSCollectionView.h"
 #import "PSCollectionViewCell.h"
+#import "PSCollectionViewLayoutAttributes.h"
+#import "PSCollectionViewItemLayoutAttributes.h"
+#import "PSCollectionViewSectionViewLayoutAttributes.h"
 
-#define kMargin 8.0
+#define kDefaultMargin 8.0
+#define kAnimationDuration 0.3f
 
-static inline NSString * PSCollectionKeyForIndex(NSInteger index) {
-    return [NSString stringWithFormat:@"%d", index];
-}
-
-static inline NSInteger PSCollectionIndexForKey(NSString *key) {
-    return [key integerValue];
-}
+#define kPSCollectionViewCellReuseBufferRows 5
 
 #pragma mark - UIView Category
 
 @interface UIView (PSCollectionView)
 
-@property(nonatomic) CGFloat left;
-@property(nonatomic) CGFloat top;
-@property(nonatomic, readonly) CGFloat right;
-@property(nonatomic, readonly) CGFloat bottom;
-@property(nonatomic) CGFloat width;
-@property(nonatomic) CGFloat height;
+@property(nonatomic, assign) CGFloat left;
+@property(nonatomic, assign) CGFloat top;
+@property(nonatomic, assign, readonly) CGFloat right;
+@property(nonatomic, assign, readonly) CGFloat bottom;
+@property(nonatomic, assign) CGFloat width;
+@property(nonatomic, assign) CGFloat height;
 
 @end
 
@@ -109,361 +107,741 @@ @implementation PSCollectionViewTapGestureRecognizer
 @end
 
 
-@interface PSCollectionView () <UIGestureRecognizerDelegate>
+@interface PSCollectionView ()
 
 @property (nonatomic, assign, readwrite) CGFloat colWidth;
 @property (nonatomic, assign, readwrite) NSInteger numCols;
-@property (nonatomic, assign) UIInterfaceOrientation orientation;
-
-@property (nonatomic, retain) NSMutableSet *reuseableViews;
-@property (nonatomic, retain) NSMutableDictionary *visibleViews;
-@property (nonatomic, retain) NSMutableArray *viewKeysToRemove;
-@property (nonatomic, retain) NSMutableDictionary *indexToRectMap;
-
-
-/**
- Forces a relayout of the collection grid
- */
-- (void)relayoutViews;
-
-/**
- Stores a view for later reuse
- TODO: add an identifier like UITableView
- */
-- (void)enqueueReusableView:(PSCollectionViewCell *)view;
-
-/**
- Magic!
- */
-- (void)removeAndAddCellsIfNecessary;
 
 @end
 
-@implementation PSCollectionView
-
-// Public Views
-@synthesize
-headerView = _headerView,
-footerView = _footerView,
-emptyView = _emptyView,
-loadingView = _loadingView;
-
-// Public
-@synthesize
-colWidth = _colWidth,
-numCols = _numCols,
-numColsLandscape = _numColsLandscape,
-numColsPortrait = _numColsPortrait,
-collectionViewDelegate = _collectionViewDelegate,
-collectionViewDataSource = _collectionViewDataSource;
-
-// Private
-@synthesize
-orientation = _orientation,
-reuseableViews = _reuseableViews,
-visibleViews = _visibleViews,
-viewKeysToRemove = _viewKeysToRemove,
-indexToRectMap = _indexToRectMap;
+@implementation PSCollectionView {
+	BOOL _batchUpdateInProgress;
+	UIInterfaceOrientation _orientation;
+	
+	BOOL _initialLayoutDataInitialized;
+	
+	NSMutableDictionary *_reusableViews;
+	
+	NSMutableArray *_colXOffsets;
+	NSInteger _numSections;
+	NSMutableArray *_sectionColumnHeights; //contains an array of arrays, first array is positioned by section number, values are the heights of each column within each section
+	NSMutableDictionary *_sectionItems; //key is section number, value is array with position is by index, value is PSCollectionViewLayoutAttribute objects
+	NSMutableArray *_sectionHeaders;
+}
 
 #pragma mark - Init/Memory
 
-- (id)initWithFrame:(CGRect)frame {
+- (id)initWithFrame:(CGRect)frame
+{
     self = [super initWithFrame:frame];
     if (self) {
         self.alwaysBounceVertical = YES;
+		
+		self.margin = kDefaultMargin;
         
         self.colWidth = 0.0;
         self.numCols = 0;
         self.numColsPortrait = 0;
         self.numColsLandscape = 0;
-        self.orientation = [UIApplication sharedApplication].statusBarOrientation;
-        
-        self.reuseableViews = [NSMutableSet set];
-        self.visibleViews = [NSMutableDictionary dictionary];
-        self.viewKeysToRemove = [NSMutableArray array];
-        self.indexToRectMap = [NSMutableDictionary dictionary];
+		self.animateLayoutChanges = YES;
+		
+		_numSections = 1;
+        _orientation = [UIApplication sharedApplication].statusBarOrientation;
+		_reusableViews = [NSMutableDictionary dictionary];
+		_sectionItems = [NSMutableDictionary dictionary];
+		_sectionHeaders = [NSMutableArray array];
+		
+		PSCollectionViewTapGestureRecognizer *recognizer = [[PSCollectionViewTapGestureRecognizer alloc] initWithTarget:self action:@selector(didSelectView:)];
+		[recognizer setCancelsTouchesInView:NO];
+		[self addGestureRecognizer:recognizer];
+		
+		[self invalidateLayout];
     }
     return self;
 }
 
-- (void)dealloc {
+- (void)dealloc
+{
     // clear delegates
     self.delegate = nil;
     self.collectionViewDataSource = nil;
     self.collectionViewDelegate = nil;
-    
-    // release retains
-    self.headerView = nil;
-    self.footerView = nil;
-    self.emptyView = nil;
-    self.loadingView = nil;
-    
-    self.reuseableViews = nil;
-    self.visibleViews = nil;
-    self.viewKeysToRemove = nil;
-    self.indexToRectMap = nil;
-    [super dealloc];
 }
 
 #pragma mark - Setters
 
+- (void)setNumColsLandscape:(NSInteger)numColsLandscape
+{
+	_numColsLandscape = numColsLandscape;
+	[self invalidateLayout];
+}
+
+- (void)setNumColsPortrait:(NSInteger)numColsPortrait
+{
+	_numColsPortrait = numColsPortrait;
+	[self invalidateLayout];
+}
+
+- (void)setMargin:(CGFloat)margin
+{
+	_margin = margin;
+	[self invalidateLayout];
+}
+
 - (void)setLoadingView:(UIView *)loadingView {
-    if (_loadingView && [_loadingView respondsToSelector:@selector(removeFromSuperview)]) {
-        [_loadingView removeFromSuperview];
-    }
-    [_loadingView release], _loadingView = nil;
-    _loadingView = [loadingView retain];
-    
-    [self addSubview:_loadingView];
+	[_loadingView removeFromSuperview];
+    _loadingView = nil;
+	
+	if (loadingView) {
+		_loadingView = loadingView;
+		[self addSubview:_loadingView];
+	}
+	
+	[self invalidateLayout];
+}
+
+- (void)setEmptyView:(UIView *)emptyView {
+	[_emptyView removeFromSuperview];
+	_emptyView = nil;
+	
+	if (emptyView) {
+		_emptyView = emptyView;
+		_emptyView.hidden = YES;
+		[self addSubview:_emptyView];
+	}
+	
+	[self invalidateLayout];
+}
+
+- (void)setHeaderView:(UIView *)headerView {
+	[_headerView removeFromSuperview];
+	_headerView = nil;
+	
+	if (headerView) {
+		_headerView = headerView;
+		[self addSubview:_headerView];
+	}
+	
+	[self invalidateLayout];
 }
 
-#pragma mark - DataSource
+- (void)setFooterView:(UIView *)footerView {
+	[_footerView removeFromSuperview];
+	_footerView = nil;
+	
+	if (footerView) {
+		_footerView = footerView;
+		[self addSubview:_footerView];
+	}
+	
+	[self invalidateLayout];
+}
+
+- (void)setFrame:(CGRect)frame
+{
+	[super setFrame:frame];
+	[self invalidateLayout];
+}
 
-- (void)reloadData {
-    [self relayoutViews];
+#pragma mark - Reset
+
+- (void)reloadData
+{
+	_initialLayoutDataInitialized = NO;
+	
+	for (NSArray *sectionItems in [_sectionItems allValues]) {
+		for (PSCollectionViewItemLayoutAttributes *attributes in sectionItems) {
+			[self enqueueReusableView:attributes.visibleCell];
+		}
+	}
+	
+	[self initializeRequiredLayoutData];
+
+    [self invalidateLayout];
+	[self setNeedsLayout];
+}
+
+- (void)resetSectionHeadersFooters
+{
+	for (PSCollectionViewSectionViewLayoutAttributes *sectionAttributes in _sectionHeaders) {
+		[sectionAttributes.view removeFromSuperview];
+	}
+	_sectionHeaders = [NSMutableArray array];
+	
+	//retrieve the section header and footers
+	for (NSUInteger i = 0; i < _numSections; i++) {
+		PSCollectionViewSectionViewLayoutAttributes *headerAttributes = [[PSCollectionViewSectionViewLayoutAttributes alloc] init];
+		if ([self.collectionViewDataSource respondsToSelector:@selector(collectionView:sectionHeaderForSection:)]) {
+			UIView *sectionHeader = [self.collectionViewDataSource collectionView:self sectionHeaderForSection:i];
+			headerAttributes.view = sectionHeader;
+			[self addSubview:sectionHeader];
+		}
+		[_sectionHeaders addObject:headerAttributes];
+	}
+}
+
+- (void)initializeRequiredLayoutData
+{
+	_sectionItems = [NSMutableDictionary dictionary];
+	
+	_numSections = [self.collectionViewDataSource numberOfSectionsInCollectionView:self];
+	//ensure there are entries for earlier sections
+	for (NSUInteger i = [_sectionColumnHeights count]; i < _numSections; i++) {
+		[_sectionColumnHeights addObject:[NSMutableArray array]];
+		[self resetColumnHeightsInSection:i];
+	}
+	
+	for (NSUInteger i = 0; i < _numSections; i++) {
+		//recreate items for the number of views that will appear in the grid
+		NSInteger numCells = [self.collectionViewDataSource collectionView:self numberOfViewsInSection:i];
+		NSMutableArray *items = [NSMutableArray arrayWithCapacity:numCells];
+		for (NSUInteger i = 0; i < numCells; i++) {
+			[items addObject:[[PSCollectionViewItemLayoutAttributes alloc] init]];
+		}
+		[_sectionItems setObject:items forKey:@(i)];
+	}
+	
+	[self resetSectionHeadersFooters];
+	
+	_initialLayoutDataInitialized = YES;
 }
 
 #pragma mark - View
 
-- (void)layoutSubviews {
+- (void)invalidateItemLayoutAttributes:(PSCollectionViewItemLayoutAttributes *)attributes
+{
+	attributes.valid = NO;
+	attributes.frame = CGRectZero;
+	attributes.previouslyVisible = NO;
+}
+
+- (void)invalidateSectionLayoutAttributes:(PSCollectionViewSectionViewLayoutAttributes *)attributes
+{
+	attributes.valid = NO;
+	attributes.previouslyVisible = NO;
+}
+
+- (void)invalidateLayout
+{
+	for (PSCollectionViewSectionViewLayoutAttributes *sectionHeader in _sectionHeaders) {
+		[self invalidateSectionLayoutAttributes:sectionHeader];
+	}
+	for (NSArray *sectionItems in [_sectionItems allValues]) {
+		[sectionItems enumerateObjectsWithOptions:NSEnumerationConcurrent usingBlock:^(PSCollectionViewItemLayoutAttributes *attributes, NSUInteger idx, BOOL *stop) {
+			[self invalidateItemLayoutAttributes:attributes];
+		}];
+	}
+	
+	self.numCols = UIInterfaceOrientationIsPortrait(_orientation) ? self.numColsPortrait : self.numColsLandscape;
+	
+	//reset the column offsets
+	_colXOffsets = nil;
+	
+	[self resetColumnHeights];
+	if (self.numCols == 0) {
+		self.colWidth = 0.0f;
+	} else {
+		self.colWidth = floorf((self.width - self.margin * (self.numCols + 1)) / self.numCols);
+	}
+	
+	[self resetSectionHeadersFooters];
+}
+
+- (void)resetColumnHeights
+{
+	//sections are assumed to be the same height, this will change as items are added to each sections
+	_sectionColumnHeights = [NSMutableArray array];
+	for (NSUInteger i = 0; i < _numSections; i++) {
+		[_sectionColumnHeights addObject:[NSMutableArray array]]; //ensure the array has a position for this section, this simplifies the resetColumnHeightsInSection method
+		[self resetColumnHeightsInSection:i];
+	}
+}
+
+- (void)resetColumnHeightsInSection:(NSUInteger)section
+{
+	//sections are assumed to be the same height, this will change as items are added to each sections
+	NSNumber *marginHeight = @(self.margin);
+	NSMutableArray *colHeights = [NSMutableArray array];
+	for (NSUInteger i = 0; i < self.numCols; i++) {
+		[colHeights addObject:marginHeight];
+	}
+	_sectionColumnHeights[section] = colHeights;
+}
+
+- (void)layoutSubviews
+{
     [super layoutSubviews];
-    
+	
     UIInterfaceOrientation orientation = [UIApplication sharedApplication].statusBarOrientation;
-    if (self.orientation != orientation) {
-        self.orientation = orientation;
-        [self relayoutViews];
-    } else {
-        [self removeAndAddCellsIfNecessary];
-    }
+    if (_orientation != orientation) {
+        _orientation = orientation;
+		[self invalidateLayout];
+	}
+	
+	[self performLayout];
 }
 
-- (void)relayoutViews {
-    self.numCols = UIInterfaceOrientationIsPortrait(self.orientation) ? self.numColsPortrait : self.numColsLandscape;
-    
-    // Reset all state
-    [self.visibleViews enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
-        PSCollectionViewCell *view = (PSCollectionViewCell *)obj;
-        [self enqueueReusableView:view];
-    }];
-    [self.visibleViews removeAllObjects];
-    [self.viewKeysToRemove removeAllObjects];
-    [self.indexToRectMap removeAllObjects];
-    
-    if (self.emptyView) {
-        [self.emptyView removeFromSuperview];
-    }
-    [self.loadingView removeFromSuperview];
-    
-    // This is where we should layout the entire grid first
-    NSInteger numViews = [self.collectionViewDataSource numberOfViewsInCollectionView:self];
-    
-    CGFloat totalHeight = 0.0;
-    CGFloat top = kMargin;
-    
-    // Add headerView if it exists
-    if (self.headerView) {
-        self.headerView.top = kMargin;
-        top = self.headerView.top;
-        [self addSubview:self.headerView];
-        top += self.headerView.height;
-        top += kMargin;
-    }
-    
-    if (numViews > 0) {
-        // This array determines the last height offset on a column
-        NSMutableArray *colOffsets = [NSMutableArray arrayWithCapacity:self.numCols];
-        for (int i = 0; i < self.numCols; i++) {
-            [colOffsets addObject:[NSNumber numberWithFloat:top]];
-        }
-        
-        // Calculate index to rect mapping
-        self.colWidth = floorf((self.width - kMargin * (self.numCols + 1)) / self.numCols);
-        for (NSInteger i = 0; i < numViews; i++) {
-            NSString *key = PSCollectionKeyForIndex(i);
-            
-            // Find the shortest column
-            NSInteger col = 0;
-            CGFloat minHeight = [[colOffsets objectAtIndex:col] floatValue];
-            for (int i = 1; i < [colOffsets count]; i++) {
-                CGFloat colHeight = [[colOffsets objectAtIndex:i] floatValue];
-                
-                if (colHeight < minHeight) {
-                    col = i;
-                    minHeight = colHeight;
-                }
-            }
-            
-            CGFloat left = kMargin + (col * kMargin) + (col * self.colWidth);
-            CGFloat top = [[colOffsets objectAtIndex:col] floatValue];
-            CGFloat colHeight = [self.collectionViewDataSource heightForViewAtIndex:i];
-            if (colHeight == 0) {
-                colHeight = self.colWidth;
-            }
-            
-            if (top != top) {
-                // NaN
-            }
-            
-            CGRect viewRect = CGRectMake(left, top, self.colWidth, colHeight);
-            
-            // Add to index rect map
-            [self.indexToRectMap setObject:NSStringFromCGRect(viewRect) forKey:key];
-            
-            // Update the last height offset for this column
-            CGFloat test = top + colHeight + kMargin;
-            
-            if (test != test) {
-                // NaN
-            }
-            [colOffsets replaceObjectAtIndex:col withObject:[NSNumber numberWithFloat:test]];
-        }
-        
-        for (NSNumber *colHeight in colOffsets) {
-            totalHeight = (totalHeight < [colHeight floatValue]) ? [colHeight floatValue] : totalHeight;
-        }
-    } else {
-        totalHeight = self.height;
-        
-        // If we have an empty view, show it
-        if (self.emptyView) {
-            self.emptyView.frame = CGRectMake(kMargin, top, self.width - kMargin * 2, self.height - top - kMargin);
-            [self addSubview:self.emptyView];
-        }
-    }
-    
-    // Add footerView if exists
-    if (self.footerView) {
-        self.footerView.top = totalHeight;
-        [self addSubview:self.footerView];
-        totalHeight += self.footerView.height;
-        totalHeight += kMargin;
-    }
-    
-    self.contentSize = CGSizeMake(self.width, totalHeight);
-    
-    [self removeAndAddCellsIfNecessary];
-}
-
-- (void)removeAndAddCellsIfNecessary {
-    static NSInteger bufferViewFactor = 5;
-    static NSInteger topIndex = 0;
-    static NSInteger bottomIndex = 0;
-    
-    NSInteger numViews = [self.collectionViewDataSource numberOfViewsInCollectionView:self];
-    
-    if (numViews == 0) return;
-    
-    // Find out what rows are visible
-    CGRect visibleRect = CGRectMake(self.contentOffset.x, self.contentOffset.y, self.width, self.height);
-    
-    // Remove all rows that are not inside the visible rect
-    [self.visibleViews enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
-        PSCollectionViewCell *view = (PSCollectionViewCell *)obj;
-        CGRect viewRect = view.frame;
-        if (!CGRectIntersectsRect(visibleRect, viewRect)) {
-            [self enqueueReusableView:view];
-            [self.viewKeysToRemove addObject:key];
-        }
-    }];
-    
-    [self.visibleViews removeObjectsForKeys:self.viewKeysToRemove];
-    [self.viewKeysToRemove removeAllObjects];
-    
-    if ([self.visibleViews count] == 0) {
-        topIndex = 0;
-        bottomIndex = numViews;
-    } else {
-        NSArray *sortedKeys = [[self.visibleViews allKeys] sortedArrayUsingComparator:^(id obj1, id obj2) {
-            if ([obj1 integerValue] < [obj2 integerValue]) {
-                return (NSComparisonResult)NSOrderedAscending;
-            } else if ([obj1 integerValue] > [obj2 integerValue]) {
-                return (NSComparisonResult)NSOrderedDescending;
-            } else {
-                return (NSComparisonResult)NSOrderedSame;
-            }
-        }];
-        topIndex = [[sortedKeys objectAtIndex:0] integerValue];
-        bottomIndex = [[sortedKeys lastObject] integerValue];
-        
-        topIndex = MAX(0, topIndex - (bufferViewFactor * self.numCols));
-        bottomIndex = MIN(numViews, bottomIndex + (bufferViewFactor * self.numCols));
-    }
-    //    NSLog(@"topIndex: %d, bottomIndex: %d", topIndex, bottomIndex);
-    
-    // Add views
-    for (NSInteger i = topIndex; i < bottomIndex; i++) {
-        NSString *key = PSCollectionKeyForIndex(i);
-        CGRect rect = CGRectFromString([self.indexToRectMap objectForKey:key]);
-        
-        // If view is within visible rect and is not already shown
-        if (![self.visibleViews objectForKey:key] && CGRectIntersectsRect(visibleRect, rect)) {
-            // Only add views if not visible
-            PSCollectionViewCell *newView = [self.collectionViewDataSource collectionView:self viewAtIndex:i];
-            newView.frame = CGRectFromString([self.indexToRectMap objectForKey:key]);
-            [self addSubview:newView];
-            
-            // Setup gesture recognizer
-            if ([newView.gestureRecognizers count] == 0) {
-                PSCollectionViewTapGestureRecognizer *gr = [[[PSCollectionViewTapGestureRecognizer alloc] initWithTarget:self action:@selector(didSelectView:)] autorelease];
-                gr.delegate = self;
-                [newView addGestureRecognizer:gr];
-                newView.userInteractionEnabled = YES;
-            }
-            
-            [self.visibleViews setObject:newView forKey:key];
-        }
-    }
+- (void)performLayout
+{
+	if (_initialLayoutDataInitialized == NO) {
+		[self initializeRequiredLayoutData];
+	}
+	
+	__block BOOL recalculateContentSize = NO;
+	
+	//layout header
+	CGSize headerSize = [self.headerView sizeThatFits:CGSizeMake(self.width, CGFLOAT_MAX)];
+	if (self.headerView.height != headerSize.height) {
+		self.headerView.height = headerSize.height;
+		self.headerView.width = self.width;
+		
+		//since the height was changed, the layout needs to be adjusted to handle it
+		[self invalidateLayout];
+		recalculateContentSize = YES;
+	}
+	
+	//handle displaying and hiding the empty view
+	if (self.emptyView) {
+		BOOL hasItems = NO;
+		for (NSArray *sectonItems in [_sectionItems allValues]) {
+			if ([sectonItems count] > 0) {
+				hasItems = YES;
+			}
+		}
+		if (hasItems == NO) {
+			self.emptyView.frame = CGRectMake(self.margin, self.margin, self.width - self.margin * 2, self.height - self.margin * 2);
+			self.emptyView.hidden = NO;
+		} else {
+			self.emptyView.hidden = YES;
+		}
+	}
+	
+	if (_colXOffsets == nil) {
+		_colXOffsets = [NSMutableArray arrayWithCapacity:self.numCols];
+		CGFloat left = self.margin;
+		for (int i = 0; i < self.numCols; i++) {
+			[_colXOffsets addObject:@(left)];
+			left += self.colWidth + self.margin;
+		}
+	}
+	
+	//calculate the positions of all cells, but skip the cells that had no change
+	//a cell has a change if its layout is marked as invalid
+	for (NSUInteger section = 0; section < _numSections; section++) {
+		NSNumber *sectionNumber = @(section);
+		
+		//layout the section header
+		PSCollectionViewSectionViewLayoutAttributes *sectionHeaderAttributes = [self sectionHeaderAttributesForSection:section];
+		if (sectionHeaderAttributes.view && sectionHeaderAttributes.valid == NO) {
+			UIView *sectionHeader = sectionHeaderAttributes.view;
+			CGSize headerSize = [sectionHeader sizeThatFits:CGSizeMake(self.width, CGFLOAT_MAX)];
+			CGFloat yOffset = [self yOffsetForBeginningOfSection:section];
+			CGRect frame = CGRectMake(CGRectGetMinX(self.bounds), yOffset, self.width, headerSize.height);
+			sectionHeaderAttributes.valid = YES;
+			
+			//animations shouldn't happen if the section header hasn't had a frame yet
+			if (self.animateLayoutChanges && sectionHeaderAttributes.previouslyVisible && CGRectEqualToRect(sectionHeader.frame, CGRectZero) == NO) {
+				[UIView animateWithDuration:kAnimationDuration animations:^{
+					sectionHeader.frame = frame;
+				}];
+			} else {
+				[UIView setAnimationsEnabled:NO];
+				sectionHeader.frame = frame;
+				[UIView setAnimationsEnabled:YES];
+			}
+			sectionHeaderAttributes.previouslyVisible = YES;
+			
+			recalculateContentSize = YES;
+		}
+		
+		//layout the section items
+		NSMutableArray *sectionItems = _sectionItems[sectionNumber];
+		[sectionItems enumerateObjectsUsingBlock:^(PSCollectionViewItemLayoutAttributes *itemAttributes, NSUInteger idx, BOOL *stop) {
+			if (itemAttributes.valid == NO) {
+				NSIndexPath *indexPath = [NSIndexPath indexPathForItem:idx inSection:section];
+				
+				//ensure we have the height for this item
+				CGFloat height = itemAttributes.frame.size.height;
+				if (height == 0.0f) {
+					height = [self.collectionViewDataSource collectionView:self heightForViewAtIndexPath:indexPath];
+				}
+				
+				//find the shortest column
+				NSUInteger shortestColumn = [self shortestColumnInSection:section];
+				CGFloat colXOffset = [_colXOffsets[shortestColumn] floatValue];
+				CGFloat yOffset = [self yOffsetForItemInSection:section column:shortestColumn];
+				CGRect frame = CGRectMake(colXOffset, yOffset, self.colWidth, height);
+				itemAttributes.frame = frame;
+				itemAttributes.currentColumn = shortestColumn;
+				itemAttributes.valid = YES;
+				
+				//update the column heights
+				[self updateHeightOfColumn:shortestColumn inSection:section withAdditionalHeight:height + self.margin];
+				recalculateContentSize = YES;
+				
+				if (self.animateLayoutChanges && itemAttributes.previouslyVisible && itemAttributes.visibleCell) {
+					[UIView animateWithDuration:kAnimationDuration animations:^{
+						itemAttributes.visibleCell.frame = itemAttributes.frame;
+					}];
+				} else {
+					[UIView setAnimationsEnabled:NO];
+					itemAttributes.visibleCell.frame = itemAttributes.frame;
+					[UIView setAnimationsEnabled:YES];
+				}
+			}
+		}];
+	};
+	
+	
+	//Lays out items that are now visible and hides cells that are no longer visible
+	CGRect visibleRect = CGRectMake(self.contentOffset.x, self.contentOffset.y, self.width, self.height);
+	[_sectionItems enumerateKeysAndObjectsUsingBlock:^(NSNumber *sectionNumber, NSArray *sectionItems, BOOL *stop) {
+		for (NSUInteger i = 0; i < [sectionItems count]; i++) {
+			PSCollectionViewItemLayoutAttributes *itemAttributes = sectionItems[i];
+			BOOL visibleCell = CGRectIntersectsRect(visibleRect, itemAttributes.frame);
+			if (visibleCell == NO && itemAttributes.visibleCell) {
+				//Cell isn't visible, hide it
+				[self enqueueReusableView:itemAttributes.visibleCell];
+				itemAttributes.visibleCell = nil;
+			} else if (visibleCell && itemAttributes.visibleCell == nil) {
+				//Cell is now visible, add it in
+				NSIndexPath *indexPath = [NSIndexPath indexPathForItem:i inSection:[sectionNumber integerValue]];
+				PSCollectionViewCell *newCell = [self.collectionViewDataSource collectionView:self viewAtIndexPath:indexPath];
+				itemAttributes.visibleCell = newCell;
+				[self addSubview:newCell];
+				
+				if (self.animateLayoutChanges && itemAttributes.previouslyVisible == NO) {
+					itemAttributes.previouslyVisible = YES;
+					[UIView setAnimationsEnabled:NO];
+					newCell.frame = itemAttributes.frame;
+					newCell.alpha = 0.0f;
+					[UIView setAnimationsEnabled:YES];
+					[UIView animateWithDuration:kAnimationDuration delay:0.0f options:UIViewAnimationOptionAllowUserInteraction animations:^{
+						newCell.alpha = 1.0f;
+					} completion:nil];
+				} else {
+					[UIView setAnimationsEnabled:NO];
+					newCell.frame = itemAttributes.frame;
+					[UIView setAnimationsEnabled:YES];
+				}
+			}
+		}
+	}];
+	
+	//get the height of the longest column in the last section
+	CGFloat availableHeight = self.height;
+	if (_numSections > 0) {
+		NSUInteger lastSection = _numSections - 1;
+		NSUInteger longestColumnInSection = [self longestColumnInSection:lastSection];
+		CGFloat longestColumnHeight = [self yOffsetForItemInSection:lastSection column:longestColumnInSection];
+		availableHeight -= longestColumnHeight;
+	}
+	if (availableHeight <= 0.0f) {
+		availableHeight = CGFLOAT_MAX;
+	}
+	CGSize footerSize = [self.footerView sizeThatFits:CGSizeMake(self.width, availableHeight)];
+	if (self.footerView.height != footerSize.height) {
+		self.footerView.height = footerSize.height;
+		recalculateContentSize = YES;
+	}
+	
+	//only update content size when it is needed
+	if (recalculateContentSize) {
+		[self updateContentSizeForColumnHeightChange];
+	}
+}
+
+- (void)insertItemAtIndexPath:(NSIndexPath *)indexPath
+{
+	PSCollectionViewItemLayoutAttributes *attributes = [[PSCollectionViewItemLayoutAttributes alloc] init];
+	
+	NSNumber *section = @(indexPath.section);
+	NSMutableArray *sectionItems = [_sectionItems objectForKey:section];
+	if (sectionItems == nil) {
+		sectionItems = [NSMutableArray array];
+		[_sectionItems setObject:sectionItems forKey:section];
+	}
+	[sectionItems insertObject:attributes atIndex:indexPath.item];
+	
+	[self invalidateLayoutOfItemsAfterIndexPath:indexPath];
+	
+	//erform layout if not in a batch update
+	if (_batchUpdateInProgress == NO) {
+		[self performLayout];
+	}
+}
+
+- (void)removeItemAtIndexPath:(NSIndexPath *)indexPath
+{
+	NSNumber *section = @(indexPath.section);
+	NSMutableArray *sectionItems = [_sectionItems objectForKey:section];
+	if (sectionItems) {
+		PSCollectionViewItemLayoutAttributes *attributes = sectionItems[indexPath.item];
+		[self enqueueReusableView:attributes.visibleCell];
+		
+		[sectionItems removeObjectAtIndex:indexPath.item];
+		[self invalidateLayoutOfItemsAfterIndexPath:indexPath];
+		
+		//perform layout if not in a batch update
+		if (_batchUpdateInProgress == NO) {
+			[self performLayout];
+		}
+	}
+}
+
+- (void)performBatchUpdates:(void (^)(void))updates completion:(void (^)(void))completion
+{
+	_batchUpdateInProgress = YES;
+	if (updates) {
+		updates();
+	}
+	//perform layout to apply the changes
+	[self performLayout];
+	_batchUpdateInProgress = NO;
+	if (completion) {
+		completion();
+	}
+}
+
+- (void)invalidateLayoutOfItemsAfterIndexPath:(NSIndexPath *)indexPath
+{
+	//invalidate all section headers for all subsequent sections
+	for (NSUInteger section = indexPath.section + 1; section < [_sectionHeaders count]; section++) {
+		PSCollectionViewSectionViewLayoutAttributes *sectionHeader = _sectionHeaders[section];
+		[self invalidateSectionLayoutAttributes:sectionHeader];
+	}
+	
+	[_sectionItems enumerateKeysAndObjectsUsingBlock:^(NSNumber *sectionNumber, NSMutableArray *sectionItems, BOOL *stop) {
+		NSInteger section = [sectionNumber integerValue];
+		if (section > indexPath.section) {
+			//invalidate all items in this section
+			//the column heights don't need to be invalidated since the section as a whole will be moved
+			for (PSCollectionViewItemLayoutAttributes *attributes in sectionItems) {
+				[self invalidateItemLayoutAttributes:attributes];
+			}
+			[self resetColumnHeightsInSection:section];
+		} else if (indexPath.section == section) {
+			//invalidate only items after this item
+			for (int i=indexPath.item; i < [sectionItems count]; i++) {
+				PSCollectionViewItemLayoutAttributes *attributes = sectionItems[i];
+				[self invalidateItemLayoutAttributes:attributes];
+			}
+			[self resetColumnHeightsInSection:section];
+		}
+	}];
+	
+	//get the max Y values from the previous elements in each column (only need to get numCols number of elements)
+	//this does not update the content size since that will be done in performLayout once all the batched changes are applied
+	//calculate until all columns have been updated
+	NSMutableIndexSet *completedColumns = [NSMutableIndexSet indexSet];
+	NSInteger i = indexPath.item - 1;
+	NSMutableArray *sectionItems = [_sectionItems objectForKey:@(indexPath.section)];
+	CGFloat yOffsetOfSection = [self yOffsetForBeginningOfSection:indexPath.section];
+	while (i >= 0) {
+		PSCollectionViewItemLayoutAttributes *attributes = sectionItems[i];
+		if (attributes.valid && [completedColumns containsIndex:attributes.currentColumn] == NO) {
+			PSCollectionViewSectionViewLayoutAttributes *sectionHeader = [self sectionHeaderAttributesForSection:indexPath.section];
+			
+			NSMutableArray *colHeights = _sectionColumnHeights[indexPath.section];
+			CGFloat height = CGRectGetMaxY(attributes.frame) - yOffsetOfSection;
+			colHeights[attributes.currentColumn] = @(height - sectionHeader.view.height + self.margin);
+			[completedColumns addIndex:attributes.currentColumn];
+		}
+		//if all columns have been updated, stop checking
+		if ([completedColumns count] == self.numCols) {
+			break;
+		}
+		
+		i--;
+	}
+}
+
+- (void)updateContentSizeForColumnHeightChange
+{
+	//calculate the height of all combined sections
+	CGFloat totalHeight = 0.0f;
+	
+	if (self.headerView) {
+		totalHeight += self.headerView.height;
+	}
+	
+	//heights of all sections
+	for (NSUInteger i = 0; i < _numSections; i++) {
+		totalHeight += [self heightOfSection:i];
+	}
+	
+	if (self.footerView) {
+		//position the footer view correctly
+		self.footerView.frame = CGRectMake(0, totalHeight, self.width, self.footerView.height);
+		
+		totalHeight += self.footerView.frame.size.height;
+	}
+	self.contentSize = CGSizeMake(self.width, totalHeight);
+}
+
+#pragma mark - Helpers
+
+- (PSCollectionViewSectionViewLayoutAttributes *)sectionHeaderAttributesForSection:(NSUInteger)section
+{
+	if (section < [_sectionHeaders count]) {
+		return _sectionHeaders[section];
+	}
+	return nil;
+}
+
+- (CGFloat)heightOfSection:(NSUInteger)section
+{
+	CGFloat height = 0.0f;
+	
+	PSCollectionViewSectionViewLayoutAttributes *header = [self sectionHeaderAttributesForSection:section];
+	if (header.view) {
+		height += header.view.height;
+	}
+	
+	height += [self heightOfLongestColumnInSection:section];
+	
+	return height;
+}
+
+- (CGFloat)yOffsetForBeginningOfSection:(NSUInteger)section
+{
+	//the yoffset is the height of all previous sections, plus the height of the column in the current section
+	CGFloat height = 0.0f;
+	
+	//collection view header
+	if (self.headerView) {
+		height += self.headerView.height;
+	}
+	
+	//add the heights of all previous sections
+	if (section > 0) {
+		for (NSUInteger i = 0; i < section; i++) {
+			height += [self heightOfSection:i];
+		}
+	}
+	
+	return height;
+}
+
+- (CGFloat)yOffsetForItemInSection:(NSUInteger)section column:(NSUInteger)column
+{
+	//the yoffset is the height of all previous sections, plus the height of the column in the current section
+	CGFloat height = [self yOffsetForBeginningOfSection:section];
+	
+	//section header height
+	PSCollectionViewSectionViewLayoutAttributes *sectionHeaderAttributes = [self sectionHeaderAttributesForSection:section];
+	if (sectionHeaderAttributes.view) {
+		height += sectionHeaderAttributes.view.height;
+	}
+	
+	NSArray *columnHeights = _sectionColumnHeights[section];
+	height += [columnHeights[column] floatValue];
+	return height;
+}
+
+- (void)updateHeightOfColumn:(NSInteger)column inSection:(NSUInteger)section withAdditionalHeight:(CGFloat)height
+{
+	NSMutableArray *columnHeights = _sectionColumnHeights[section];
+	NSNumber *currentHeight = columnHeights[column];
+	columnHeights[column] = @([currentHeight floatValue] + height);
+}
+
+- (NSUInteger)shortestColumnInSection:(NSUInteger)section
+{
+	NSInteger col = 0;
+	NSMutableArray *sectionColumnHeights = _sectionColumnHeights[section];
+	CGFloat minHeight = [sectionColumnHeights[col] floatValue];
+	for (int i = 1; i < [sectionColumnHeights count]; i++) {
+		CGFloat colHeight = [sectionColumnHeights[i] floatValue];
+		if (colHeight < minHeight) {
+			col = i;
+			minHeight = colHeight;
+		}
+	}
+	return col;
+}
+
+- (NSUInteger)longestColumnInSection:(NSUInteger)section
+{
+	NSInteger col = 0;
+	NSMutableArray *columnHeights = _sectionColumnHeights[section];
+	CGFloat maxHeight = [columnHeights[col] floatValue];
+	for (int i = 1; i < [columnHeights count]; i++) {
+		CGFloat colHeight = [columnHeights[i] floatValue];
+		if (colHeight > maxHeight) {
+			col = i;
+			maxHeight = colHeight;
+		}
+	}
+	return col;
+}
+
+- (CGFloat)heightOfLongestColumnInSection:(NSUInteger)section
+{
+	NSUInteger longestColumn = [self longestColumnInSection:section];
+	return [_sectionColumnHeights[section][longestColumn] floatValue];
 }
 
 #pragma mark - Reusing Views
 
-- (PSCollectionViewCell *)dequeueReusableView {
-    PSCollectionViewCell *view = [self.reuseableViews anyObject];
-    if (view) {
-        // Found a reusable view, remove it from the set
-        [view retain];
-        [self.reuseableViews removeObject:view];
-        [view autorelease];
-    }
-    
-    return view;
+- (PSCollectionViewCell *)dequeueReusableViewWithIdentifier:(NSString *)reuseIdentifier
+{
+	if ([reuseIdentifier length] == 0) {
+		return nil;
+	}
+	
+	NSMutableSet *reusableViewsForIdentifier = [_reusableViews objectForKey:reuseIdentifier];
+	if (reusableViewsForIdentifier) {
+		PSCollectionViewCell *view = [reusableViewsForIdentifier anyObject];
+		if (view) {
+			// Found a reusable view, remove it from the set
+			[reusableViewsForIdentifier removeObject:view];
+			return view;
+		}
+	}
+	return nil;
 }
 
-- (void)enqueueReusableView:(PSCollectionViewCell *)view {
-    if ([view respondsToSelector:@selector(prepareForReuse)]) {
-        [view performSelector:@selector(prepareForReuse)];
-    }
+- (void)enqueueReusableView:(PSCollectionViewCell *)view
+{
+	if (view == nil) {
+		return;
+	}
+	
+	[view prepareForReuse];
     view.frame = CGRectZero;
-    [self.reuseableViews addObject:view];
+	view.alpha = 1.0f;
+	
+	NSMutableSet *reusableViewsForIdentifier = [_reusableViews objectForKey:view.reuseIdentifier];
+	if (reusableViewsForIdentifier == nil && [view.reuseIdentifier length] > 0) {
+		[_reusableViews setObject:[NSMutableSet set] forKey:view.reuseIdentifier];
+	}
+	[reusableViewsForIdentifier addObject:view];
     [view removeFromSuperview];
 }
 
 #pragma mark - Gesture Recognizer
 
-- (void)didSelectView:(UITapGestureRecognizer *)gestureRecognizer {    
-    NSString *rectString = NSStringFromCGRect(gestureRecognizer.view.frame);
-    NSArray *matchingKeys = [self.indexToRectMap allKeysForObject:rectString];
-    NSString *key = [matchingKeys lastObject];
-    if ([gestureRecognizer.view isMemberOfClass:[[self.visibleViews objectForKey:key] class]]) {
-        if (self.collectionViewDelegate && [self.collectionViewDelegate respondsToSelector:@selector(collectionView:didSelectView:atIndex:)]) {
-            NSInteger matchingIndex = PSCollectionIndexForKey([matchingKeys lastObject]);
-            [self.collectionViewDelegate collectionView:self didSelectView:(PSCollectionViewCell *)gestureRecognizer.view atIndex:matchingIndex];
-        }
-    }
-}
-
-- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch {
-    if (![gestureRecognizer isMemberOfClass:[PSCollectionViewTapGestureRecognizer class]]) return YES;
-    
-    NSString *rectString = NSStringFromCGRect(gestureRecognizer.view.frame);
-    NSArray *matchingKeys = [self.indexToRectMap allKeysForObject:rectString];
-    NSString *key = [matchingKeys lastObject];
-    
-    if ([touch.view isMemberOfClass:[[self.visibleViews objectForKey:key] class]]) {
-        return YES;
-    } else {
-        return NO;
-    }
+- (void)didSelectView:(UITapGestureRecognizer *)gestureRecognizer
+{
+	CGPoint tapPoint = [gestureRecognizer locationInView:self];
+	
+	__block PSCollectionViewItemLayoutAttributes *selectedCell = nil;
+	__block NSIndexPath *selectedIndexPath = nil;
+	[_sectionItems enumerateKeysAndObjectsUsingBlock:^(NSNumber *sectionNumber, NSArray *sectionItems, BOOL *stop) {
+		[sectionItems enumerateObjectsUsingBlock:^(PSCollectionViewItemLayoutAttributes *candidate, NSUInteger idx, BOOL *stop) {
+			if (candidate.valid && CGRectContainsPoint(candidate.frame, tapPoint)) {
+				selectedCell = candidate;
+				selectedIndexPath = [NSIndexPath indexPathForItem:idx inSection:[sectionNumber integerValue]];
+				*stop = YES;
+			}
+		}];
+	}];
+	
+	PSCollectionViewCell *cell = selectedCell.visibleCell;
+	if (cell) {
+		[self.collectionViewDelegate collectionView:self didSelectView:cell atIndexPath:selectedIndexPath];
+	}
 }
 
 @end
diff --git a/PSCollectionViewCell.h b/PSCollectionViewCell.h
index b37551b..24c50a3 100644
--- a/PSCollectionViewCell.h
+++ b/PSCollectionViewCell.h
@@ -25,7 +25,10 @@
 
 @interface PSCollectionViewCell : UIView
 
-@property (nonatomic, retain) id object;
+@property (nonatomic, strong) id object;
+@property (nonatomic, readonly, copy) NSString *reuseIdentifier;
+
+- (id)initWithFrame:(CGRect)frame reuseIdentifier:(NSString *)reuseIdentifier;
 
 - (void)prepareForReuse;
 - (void)fillViewWithObject:(id)object;
diff --git a/PSCollectionViewCell.m b/PSCollectionViewCell.m
index 4ffb17f..118dc80 100644
--- a/PSCollectionViewCell.m
+++ b/PSCollectionViewCell.m
@@ -23,35 +23,29 @@
 
 #import "PSCollectionViewCell.h"
 
-@interface PSCollectionViewCell ()
-
-@end
-
 @implementation PSCollectionViewCell
 
-@synthesize
-object = _object;
-
-- (id)initWithFrame:(CGRect)frame {
-    self = [super initWithFrame:frame];
-    if (self) {
-    }
-    return self;
-}
-
-- (void)dealloc {
-    self.object = nil;
-    [super dealloc];
+- (id)initWithFrame:(CGRect)frame reuseIdentifier:(NSString *)reuseIdentifier
+{
+	self = [super initWithFrame:frame];
+	if (self) {
+		_reuseIdentifier = [reuseIdentifier copy];
+	}
+	return self;
 }
 
-- (void)prepareForReuse {
+- (void)prepareForReuse
+{
+	self.object = nil;
 }
 
-- (void)fillViewWithObject:(id)object {
+- (void)fillViewWithObject:(id)object
+{
     self.object = object;
 }
 
-+ (CGFloat)heightForViewWithObject:(id)object inColumnWidth:(CGFloat)columnWidth {
++ (CGFloat)heightForViewWithObject:(id)object inColumnWidth:(CGFloat)columnWidth
+{
     return 0.0;
 }
 
diff --git a/PSCollectionViewItemLayoutAttributes.h b/PSCollectionViewItemLayoutAttributes.h
new file mode 100644
index 0000000..10854b7
--- /dev/null
+++ b/PSCollectionViewItemLayoutAttributes.h
@@ -0,0 +1,15 @@
+//
+//  PSCollectionViewItemLayoutAttributes.h
+//  ShopByShopify
+//
+//  Created by Adam Becevello on 2012-12-20.
+//  Copyright (c) 2012 Shopify Inc. All rights reserved.
+//
+
+#import "PSCollectionViewLayoutAttributes.h"
+
+@interface PSCollectionViewItemLayoutAttributes : PSCollectionViewLayoutAttributes
+
+@property (nonatomic, strong) PSCollectionViewCell *visibleCell;
+
+@end
diff --git a/PSCollectionViewItemLayoutAttributes.m b/PSCollectionViewItemLayoutAttributes.m
new file mode 100644
index 0000000..d8fe27e
--- /dev/null
+++ b/PSCollectionViewItemLayoutAttributes.m
@@ -0,0 +1,13 @@
+//
+//  PSCollectionViewItemLayoutAttributes.m
+//  ShopByShopify
+//
+//  Created by Adam Becevello on 2012-12-20.
+//  Copyright (c) 2012 Shopify Inc. All rights reserved.
+//
+
+#import "PSCollectionViewItemLayoutAttributes.h"
+
+@implementation PSCollectionViewItemLayoutAttributes
+
+@end
diff --git a/PSCollectionViewLayoutAttributes.h b/PSCollectionViewLayoutAttributes.h
new file mode 100644
index 0000000..c26164d
--- /dev/null
+++ b/PSCollectionViewLayoutAttributes.h
@@ -0,0 +1,19 @@
+//
+//  PSCollectionViewLayoutAttributes.h
+//  ShopByShopify
+//
+//  Created by Adam Becevello on 2012-12-14.
+//  Copyright (c) 2012 Shopify Inc. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+#import "PSCollectionViewCell.h"
+
+@interface PSCollectionViewLayoutAttributes : NSObject
+
+@property (nonatomic, assign) CGRect frame;
+@property (nonatomic, assign) NSUInteger currentColumn;
+@property (nonatomic, assign) BOOL valid;
+@property (nonatomic, assign) BOOL previouslyVisible;
+
+@end
diff --git a/PSCollectionViewLayoutAttributes.m b/PSCollectionViewLayoutAttributes.m
new file mode 100644
index 0000000..1efa726
--- /dev/null
+++ b/PSCollectionViewLayoutAttributes.m
@@ -0,0 +1,25 @@
+//
+//  PSCollectionViewLayoutAttributes.m
+//  ShopByShopify
+//
+//  Created by Adam Becevello on 2012-12-14.
+//  Copyright (c) 2012 Shopify Inc. All rights reserved.
+//
+
+#import "PSCollectionViewLayoutAttributes.h"
+
+@implementation PSCollectionViewLayoutAttributes
+
+- (id)init
+{
+	self = [super init];
+	if (self) {
+		self.frame = CGRectZero;
+		self.currentColumn = 0;
+		self.valid = NO;
+		self.previouslyVisible = NO;
+	}
+	return self;
+}
+
+@end
diff --git a/PSCollectionViewSectionViewLayoutAttributes.h b/PSCollectionViewSectionViewLayoutAttributes.h
new file mode 100644
index 0000000..21007aa
--- /dev/null
+++ b/PSCollectionViewSectionViewLayoutAttributes.h
@@ -0,0 +1,15 @@
+//
+//  PSCollectionViewSectionViewLayoutAttributes.h
+//  ShopByShopify
+//
+//  Created by Adam Becevello on 2012-12-20.
+//  Copyright (c) 2012 Shopify Inc. All rights reserved.
+//
+
+#import "PSCollectionViewLayoutAttributes.h"
+
+@interface PSCollectionViewSectionViewLayoutAttributes : PSCollectionViewLayoutAttributes
+
+@property (nonatomic, readwrite, strong) UIView *view;
+
+@end
diff --git a/PSCollectionViewSectionViewLayoutAttributes.m b/PSCollectionViewSectionViewLayoutAttributes.m
new file mode 100644
index 0000000..ac5df23
--- /dev/null
+++ b/PSCollectionViewSectionViewLayoutAttributes.m
@@ -0,0 +1,13 @@
+//
+//  PSCollectionViewSectionViewLayoutAttributes.m
+//  ShopByShopify
+//
+//  Created by Adam Becevello on 2012-12-20.
+//  Copyright (c) 2012 Shopify Inc. All rights reserved.
+//
+
+#import "PSCollectionViewSectionViewLayoutAttributes.h"
+
+@implementation PSCollectionViewSectionViewLayoutAttributes
+
+@end
diff --git a/README.md b/README.md
index fdb80b9..af0ecfa 100644
--- a/README.md
+++ b/README.md
@@ -4,9 +4,15 @@ It's a Pinterest style scroll view designed to be used similar to a UITableView.
 
 It supports Portrait and Landscape orientations.
 
-I built this as a hack to show my friends. Any suggestions or improvements are very welcome!
+This version is an almost complete rewrite of the layout code to support additional features such as:
+  1. Multiple sections
+  2. Section headers and footers
+  3. Improved performance and reduced memory usage, especially during fast scrolling operations.
 
-Coming soon... A fully functional demo app.
+Due to the inclusion of multiple section support, this fork is not API compatible with the original PSCollectionView found at https://github.com/ptshih/PSCollectionView.
+Thanks to Peter Shih (https://github.com/ptshih) for writing the original PSCollectionView which forms the basis of this version.
+
+The rest of this README is the same as the README in the original PSCollectionView repository.
 
 What is PSCollectionViewCell?
 ---
@@ -32,9 +38,7 @@ It shows an example of using PSCollectionView and a subclass of PSCollectionView
 
 ARC
 ---
-PSCollectionView, by default, is not ARC ready.
-
-However, there is an 'arc' branch that has been converted for use with ARC projects.
+This version of PSCollectionView is ARC ready.
 
 How to use:
 ---
@@ -128,4 +132,4 @@ THE SOFTWARE.
 
 Questions?
 ---
-Feel free to send me an email if you have any questions implementing PSCollectionView!
\ No newline at end of file
+Feel free to send me an email if you have any questions implementing PSCollectionView!