Illusion #131 : The cat is dreaming about its lunch. Click the image and stare at the fish for 30 seconds, and then click the image again.
There are many different types of illusion. Physical illusions are illusions where something has happened before the light reaches the eye, such as a rainbow. Physiological illusions are the effects on the brain by stimulation of a specific type such as brightness, colour and movement. Visual cognitive illusions are those that go against what is perceived as logic, and can continue to confuse even when the trick is known.