NIST researchers have demonstrated a minuscule atomic clock with inner workings about the size of a grain of rice and potential applications in atomically precise timekeeping in portable, battery-powered devices for secure wireless communications, more precise navigation, and other applications. The "physics package" of the clock, believed to be the smallest in the world, is about 1.5 millimeters on a side and about 4 millimeters tall, consumes less than 75 thousandths of a watt, and has a...