UICollectionView - Downloading images and effective reloading of data, like Instagram

Question

I noticed that apps like Intagram uses UICollectionViews to display the feed of photos. I also noticed that the cells for these photos is somehow placed on screen

Answer 1

use

[self.collectionView reloadItemsAtIndexPaths:[NSArray arrayWithObject:indexPath]];

instead of

[self.collectionView reloadData];

here indexPath is the NSIndexPath Object for the corresponding UICollectionViewCell Object