A stereogram is a form of optical illusion that creates a three-dimensional image from a two-dimensional picture. There are several synonyms for this word, including autostereogram, random dot stereogram, and magic eye image. The term autostereogram is often used to refer to images that are generated by a computer algorithm, while random dot stereogram is used to describe images with randomly placed dots that create the illusion of depth. Magic eye image is a popular term that is often associated with the series of books published in the 1990s that featured stereograms. Other synonyms for stereogram include 3D image, 3D picture, and hologram.