The eye gets tricked to see a black dot when it’s actually white:
Black Dot illusion

Look at the image - do you see the box popping out?
Box Coming out Illusion
 
What is wrong with this picture? The lines don’t bend in any directions they are straight.
Bending Black and White
 
Now focus on the circle in the middle of the circle. The move your head back from the screen and forward again and the circles move!
 
This pictures shows four cubes coming out of the canvas. But that’s just an illusion as well.
 
This one is really creepy to look at IMHO. They aren’t moving I swear! Look at the marks to see the doesn’t move at all.
Spinning Wheels illusion
 
This one ain’t moving either…
Moving Waves illusion
 
Take a long good stare at this picture. Focus on the four dots in the middle, then after 30 seconds move your eyes to an empty surface like your wall - what do you see?
Jesus Illusion
 
An oldie but goldie. Click for a larger picture
Yorick's Skull Illusion
 
Left Brain Right Brain

Finally - it’s true don’t be afraid of monsters it really isn’t one at the end.

Stumble it!