The Necker cube is a simple wireframe drawing of a cube that can be perceived in two different orientations. It was first introduced by the Swiss crystallographer Louis Necker in 1832. The cube is an example of a reversible figure, meaning that viewers can switch their perception between the two possible 3D interpretations. This optical illusion highlights how our brains interpret visual information. When looking at the Necker cube, the mind alternates between seeing the cube from different perspectives, demonstrating the complexity of visual perception and how our brains construct reality from two-dimensional images.