In grade school, you made art (or at least ashtrays) by gluing tiles together in a matrix. You could even make a recognizable picture if you had the right colors. Photoshop and other bitmap art programs help you create the most detailed tile art ever made! Each bitmap file is made up of tiny square tiles called "pixels." The pixels are so small (72 per inch on standard computer screen, 1080 per inch on HD screens, and anywhere from 300 to 1600 per inch in print) that the eye blends them together, and so numerous (a high resolution print contains several million, and a large-screen HD image may contain billions) that complex, photographic detail is maintained. In the past, bitmapped files had to be "flattened" to a single layer, which meant text could no longer be selected and some elements would appear slightly blurred. But the new Adobe Creative Suite programs allow you to use multi-layer bitmap files all the way through production, and enjoy the best of both worlds.