Lean back a bit and stare at the dot far awhile without moving your eyes or your head. The dot will gradually fade into the field of green. The dot many fad more rapidly if they stare blankly at the edge of the square. As soon as you move your head or eyes, notice that the blue reappears.

What's Going On?

Although you may not know, your eye is always making tiny jittery movements. Each time your eye moves it receives new information and sends it to your brain. This constant new information is what you need to see images.

You may notice that although the dot fades, just about everything else in your field of vision remains clear. That's because everything else you see has distinct edges.