In the past 50 years, computers have shrunk from room-size mainframes to lightweight handhelds. This fantastic miniaturization is primarily the result of high-volume nanoscale manufacturing. While this technology has predominantly been applied to logic and memory, it's now being used to create advanced microelectromechanical systems using both top-down and bottom-up processes. One possible outcome of continued progress in high-volume nanoscale assembly is the ability to inexpensively produce millimeter-scale units that integrate computing, sensing, actuation, and locomotion mechanisms. A collection of such units can be viewed as a form of programmable matter.