A stereogram is a flat image that when viewed properly produces a magical 3D result. Some people will tell you that they simply cannot see these kinds of images. I recently had someone tell me that he has not been able to get these to work and he has been trying since the 1990s when Magic Eye started producing posters for sale in shopping malls. The truth is that almost everyone can see them (if they try hard enough!). An obvious exception would be someone who has a serious vision problem.
Stare at the following image created by Gary W. Priester and let your eyes relax while focusing on the pattern. You might start to perceive some depth and if you are doing it correctly or have done this before, a hidden image of a butterfly will begin to emerge.
To view more stereograms or to learn how you can have a custom stereogram made with your own message or logo hidden in it, please visit eyeTricks 3D Stereograms.