The zoetrope, invented by William George Horner circa 1833 as an animation device before movie films, is a cylinder with vertical slits cut on its sides. To experience this early motion picture projector, look at the pictures through the slits as they move across. When the zoetrope is spun around, it creates a rapid succession of images, giving the illusion of motion—this stroboscopic effect was the fundamental idea inspiring the development of motion pictures.