Embedded in homes, offices, cars, and factories, thousands of tiny computerized sentries could track inventories, monitor electricity use, and even detect ground vibrations and toxic gases to provide early warning of earthquakes and chemical spills. But how are researchers turning this vision into reality? "What we bring to the table is, we make real products," says Sokwoo Rhee, chief technology officer of Millennial Net, an MIT spinoff. By designing ultralow-power, postage-stamp-size hardware and smart networking software for sensors, he says, his team is building the "Swiss Army knife of wireless applications" that can go anywhere, anytime. Millennial Net's products are already being used to automate and report meter readings, detect carbon monoxide and turn on ventilation fans in parking garages, and track temperature-sensitive items like food and drink in transport. The goal is to be integrated into "millions of devices by 2007," says Rhee, so that a sensor in a streetlight, say, could alert you to weather or traffic problems via your cell phone. At Millennial Net's headquarters in Cambridge, MA, Rhee showed TR associate editor Gregory T. Huang how to assemble a wireless mesh of networked sensors-and deploy them to do work in the real world.