Shadow Illusion

The checker shadow illusion is an optical illusion published by Edward H. Adelson, professor of vision science at MIT, in 1995. It showcases the relative and context-dependent nature of human color perception.

The steel balls sit on two checkerboard fields that appear to be different shades, but despite the illusion, the fields beneath the balls are exactly the same color; our brain is tricked by the shadow and surrounding context.