Adobe Photoshop creates and edits raster graphics. Raster images (also known as bitmaps) are comprised of tiny blocks of color called pixels. When zoomed in, individual pixels can be seen forming a grid that, when zoomed out, create an image. The effect is like a pointillist painting; mere dots of color up close, but combining together to make an image from a distance. Be careful when resizing these images in Photoshop, as pixelation is a potential problem with all raster-based images.