Visual illusions cut across academic divides and popular interests: on the one hand, illusions provide entertainment as curious tricks of the eye; on the other hand, scientific research related to illusory phenomena has given generations of scientists and artists deep insights into the brain and principles of mind and consciousness. Numerous thinkers (including Aristotle, Descartes, Da Vinci, Escher, Goethe, Galileo, Helmholtz, Maxwell, Newton, and Wittgenstein) have been lured by the apparent simplicity of illusions and the promise that illusory phenomena can elucidate the puzzling relationship between the physical world and our perceptual reality. Over the past thirty years, advances in imaging and electrophysiology has dramatically expanded the range of illusions and enabled new forms of analysis, thereby creating new and exciting ways to consider how the brain constructs our perceptual world.