The Smart Dust project is probing microfabrication technology's limitations to determine whether an autonomous sensing, computing, and communication system can be packed into a cubic millimeter mote (a small particle or speck) to form the basis of integrated, massively distributed sensor networks. Although we've chosen a somewhat arbitrary size for our sensor systems, exploring microfabrication technology's limitations is our fundamental goal. Because of its discrete size, substantial functionality, connectivity, and anticipated low cost, Smart Dust will facilitate innovative methods of interacting with the environment, providing more information from more places less intrusively.