Imagine a clock that doesn't have electricity, but its hands and gears spin on their own for all eternity. In a new study, physicists at the University of Colorado Boulder have used liquid crystals, the same materials that are in your phone display, to create such a clock—or, at least, as close as humans can get to that idea. The team's advancement is a new example of a "time crystal." That's the name for a curious phase of matter in which the pieces, such as atoms or other particles, exist in constant motion.