We all know that what is an Optical Illusion, it is visually perceived images that differ from objective reality. The information gathered by the eye is processed in the brain to give a percept that does not tally with a physical measurement of the stimulus source.There is one such Optical Illusion shown below-
To see an Optical Illusion Effect in it, just see the Plus sign in between the circles, concentrate on it and do not move, you will see the green colour dots will make the circles go vanished. But if you will not concentrate in center you will see that green dots are simply moving around and not effecting the pink dots. Just give it a try.