And then they tried a new concept that would allow people to scroll through photos vertically, showing the most recent post first, like Twitter. All of the photos would use as few pixels as possible, so that they would load quickly, helping solve problem number one—only 306 pixels across, the minimum required to display a photo on an iPhone with 7-pixel borders on each side. The photos would be square, giving users the same creative constraint for photography as Systrom’s teacher in Florence gave him.
