We got up pretty close to the iPhone 4 's retina display in our review , but we can't say we got quite as close as PhD candidates Ryan White and Bryan Gauntt of Penn State University, who have kindly provided us with some images of the screen under a microscope (along with an iPhone 3G for comparison). According to their measurements, the iPhone 3G's pixels measure 13 x 40 microns, while the iPhone 4's measure 6.5 x 20 microns, which adds up to exactly four times as many pixels. As impressive as sounds that sounds, however, it's the pictures that really tell the story -- hit up the gallery below to check them out.