Microelectromechanical systems (MEMS) combine highly miniaturized electrical and mechanical components (parts) on a special type of computer chip. MEMS range from such simple machines as levers to complicated safety locks that prevent nuclear weapons from exploding accidentally. Some MEMS devices are no larger than a grain of sand. They are usually measured in micrometers. A micrometer is 0.001 millimeter or 1/25,400 of an inch.