Spinning Red Stripes Optical Illusion
Stare at the black dot in the center of this image and watch the red stripes spin. At first, they should appear to be moving in a clockwise direction. After a short while, however, they will suddenly appear to reverse and start moving counter-clockwise.
If you lie on the ground and look directly up at a ceiling fan, you will notice the same type of effect. For a similar effect, you might want to revisit the classic spinning dancer illusion where a dancing woman starts off spinning in one direction and then ends up spinning in the opposite direction.
One of the earliest optical illusions, known as the Troxler Effect, was another illusion where you stare at a dot in the center of a circle. When you do so, the blue circle begins to slowly fade away.