Researchers have created flat sheets of composite material that can fold themselves into toy boats, tents, and even paper airplanes. Based on the ancient art of origami, the sheets are edged by foil actuators -- thin, solid-state motors -- that contract or expand when they receive an electric current from flexible electronic circuits embedded in the sheets. After they achieve their preprogrammed shape, the sheets are held in place by tiny magnets on the edges of the fold joints.