How did I not know about this before! This is amazing, but you have to have some patience!
A stereogram is a pair of two-dimensional panels depicting the view of a scene or an object from the vantage points of the right and left eyes. Basically, if you can train your eyes to look at the images correctly, you can see in 3-dimensions without the need for 3d glasses.
In order to see in 3d, you must follow these instructions very carefully: http://www.2eyephotography.com/
Give it some patience, and you will be able to do it. It’s kind of like Magic Eye. The key is to make sure the middle image is the same size as the images on the sides, then just keep focusing back and forth between your pencil and that middle image until you can keep the middle image in focus. Then voila! You can see in 3d!
Try not to get frustrated, and take a break if you are getting a headache, but it will be awesome when you can see the depth.