Optical illusions!

Because we love them! (At least I do ^^)

Don't worry, I've checked them all very carefully, they are not animated gifs but real optical illusions. You can actually stop the "motion" if you concentrate hard and stop moving your eyes. Most of these illusions actually depend on the brain's own anticipations and the approximative visual information of the peripheral sight. By unconsciously/ mechanically sweeping over the image while looking at it, you merely imprint the approximative vision in your very short-term memory, the brain easily modifies this vague information, and holds it for hard fact, in order to fit the conclusion it calculates can be drawn: motion. Colors, shapes and the different priorities subconsciously set to each of these elements define the imaginary motion more precisely (orientation, 3D conversion, etc). And there you have it!