Look closely at the picture above. What you're actually looking at is a work of art by Johannes Stotter. Despite its extremely photographic nature, it's actually a painting.
Even more shocking is the canvas isn't cloth. It's a woman covered in body paint.
Stotter's work takes advantage of the fact that our eyes skim and our brains tend to jump to conclusions. The act of seeing something begins with light rays bouncing off an object. These rays enter the eyes through the cornea, which is the clear, outer portion of the eye. The cornea then bends or refracts the light rays as they go through the black part of your eye, the pupil. The iris — the colored portion of your eye — contracts or expands to change the amount of light that goes through.
Finally, the light rays go through the lens of your eye, which changes shape to target the light towards your retina, the thin tissue at the back of your eye that is full of nerve cells that detect light. The cells in the retina, called rods and cones, turn the light into electrical signals. That gets sent through the optic nerve, where the brain interprets them.
The entire process takes about one-tenth of a second, but that's long enough to make your brain confused sometimes, evolutionary neurobiologist Mark Changizi told Discovery News.
By arranging a series of patterns, images, and colors strategically, or playing with the way an object is lit, the brain can be tricked into seeing something that isn't there. How you perceive proportion can also be altered depending on the known objects that are nearby. It's not magic — it's an optical illusion.
For example, Changizi pointed out that when we move and look at something, the image becomes a blurry line in our vision. Because our brains associate those blurred lines with motion, static pictures that feature fuzziness tend to look like they are moving at warp speed.
For the rest of the story: http://theweek.com/article/index/258473/how-optical-illusions-trick-your-brain-according-to-science