Al Seckel, formerly of the California Institute of Technology, is a leading authority on visual and other types of sensory illusions. His earlier work, The Great Book of Optical Illusions garnered rave reviews, and sold nearly 100,000 copies. He is the author of over 15 books on this subject, and has lectured extensively at many of the world's most prestigious universities. He also designs interactive galleries on illusions and perception for science museums across the country and around the world. Seckel writes an illusion column for National Geographic Kids magazine.