Magic Eye

Magic Eye is a series of books published by N.E. Thing Enterprises (renamed in 1996 to Magic Eye Inc.). The books feature autostereograms, which allow some people to see 3D images by focusing on 2D patterns. The viewer must diverge their eyes in order to see a hidden three-dimensional image within the pattern. The term "Magic Eye" has become something of a genericized trademark, often used to refer to autostereograms of any origin. The autostereogram predates the "Magic Eye" series by several years. Christopher Tyler created the first black-and-white autostereograms in 1979 with the assistance of computer programmer Maureen Clarke.
After creating its first images in 1991, creator Tom Baccei worked with Tenyo, a Japanese company that sells magic supplies. Tenyo published its first book in late 1991 titled "Miru Miru Mega Yokunaru Magic Eye" ("Your Eyesight Gets Better & Better in a Very Short Rate of Time: Magic Eye"), sending sales representatives out to street corners to demonstrate how to see the hidden image. Within a few weeks the first Japanese book became a best seller, as did the second, rushed out shortly after.
The first North American "Magic Eye" book, "Magic Eye: A New Way of Looking at the World" was released by Andrews & McMeel in 1993. According to the book's dust jacket, the images were rendered by "Salitsky Dot," a patented method. Within a year it had been followed by two sequels that were also extremely popular. The three books spent a cumulative total of 73 weeks on the "New York Times" Bestseller List. Dozens of other books and other products have been released since then; Magic Eye stereograms have been featured on postcards, mousepads, lunch boxes, cereal boxes and even neckties. Magic Eye stereograms have also been featured in a weekly newspaper comic panel syndicated by Universal Press Syndicate.
The Magic Eye images have a horizontally repeating pattern which differs slightly with each repetition, therefore giving the illusion of depth when each eye focuses on a different part of the pattern. The stereograms were created using a patented process that allows colorful patterns to be used in creating the final images.
Magic Eye stereograms have been used by orthoptists and vision therapists in the treatment of some binocular vision and accommodative disorders.
In popular culture.
Dave Matthews Band's 1993 debut album, "Remember Two Things", features a stereogram of a hand giving a peace sign.
The books were featured in an episode of "Ellen" (season 2, episode 4). Ellen fails to see the stereograms and the episode concludes with her saying "My name is Ellen and I can't Magic Eye". 
A stereogram poster is also featured in a 1994 episode of "Seinfeld", "The Gymnast", although it is referred to as "3-D art" that is made by "BIG computers". In the episode, Elaine's boss becomes obsessed with the poster and spends days struggling to see the image of a spaceship in the patterns, neglecting an important business merger he was overseeing.
It was also featured in season 1 episode 6 of "Friends", "The One with the Butt", where Ross cannot spot the Statue of Liberty.
There is also a running gag in the 1995 Kevin Smith film "Mallrats" where a character named Willam, played by Ethan Suplee, cannot see a sailboat.
In promotion for "Captain Marvel", which takes place in 1995, the official Twitter for the film posted several stereograms that feature characters from the film.