One of my favorite things that was shown to me during my elementary age years was an optical illusion. It was the very famous Rubin Vase (pictured below) which you can see in either two ways - as a vase or as two faces that are facing each other.
Thats really cool ! Stare at the red dot on the girl’s nose for 30 seconds. Turn your eyes to a plain surface (your ceiling or blank wall). Blink repeatedly and quickly This is awesome! i saw the picture of the girl in color!