Humans have binocular vision, meaning we have two eyes. Since our eyes are each positioned differently in our heads, each sees a slightly different perspective. But when used together and aided by our brains, we end up perceiving depth and notice even more details due to something called binocular summation. Using 3D glasses and specially designed images called anaglyphs, we can recreate a similar viewing effect.
Anaglyphs are pictures made by superimposing two images of the same object (taken from slightly different perspectives) in two complementary colors—usually red-blue. When viewed with spectrally opposed glasses, like the ones you just made, the anaglyph appears three-dimensional. In this case, the red filter over the left eye perceives the red in the image as white and the blue within the image as black. The right eye sees just the opposite, perceiving red as black and cyan as white. Through the 3d glasses, the graduations between red and cyan are viewed as graduations of bright to dark, lending the perception of depth. When viewed together, the brain fuses the images into one, three-dimensional view.
Use Photoshop to make your own anaglyphs.