Necker Cube

Developed in 1832 by the Swiss crystallographer Louis Necker, the Necker Cube is an optical illusion that demonstrates how the brain works on a sub-conscious level independently of thought. If you stare at the wire frame model of a cube for a while, it appears to flip its orientation between two possible interpretations of the picture. This phenomenon has served as evidence of the human brain operating as a neural network with two distinct equally possible interchangeable stable states.