Nothing quite like it had ever been attempted. Deep in the California desert last March, as a few fatigues-clad U.S. MARINES stood nearby, researchers from the University of California, Berkeley, fiddled with a 1.5-meter airplane with six walnut-sized bundles of electronics ATTACHED to the undersides of its wings. Each bundle, swaddled in pink plastic, held a magnetic-field sensor, short-range radio transmitter, antenna and microprocessor run by a custom low-powered operating system dubbed "Tiny OS."

And then the remote-controlled plane, freighted with the early embodiments of a hoped-for advance in miniaturized, networked sensing, buzzed aloft, traveled about two kilometers and dropped its pink payload along a dirt road. Soon, as planned, a few trucks drove past the innocuous electronic spies. The bundles detected the trucks' magnetic fields, shared this information among themselves and beamed a report on the vehicles' location, speed and direction to the remote-controlled plane circling overhead. The aircraft, in turn, relayed the news to the researchers and soldiers waiting on the rugged terrain of the Marine Corps base in Twentynine Palms, CA.

The bundles were crude prototypes, and it took days to get even this limited experiment right. But someday thousands of similar devices-only much tinier, perhaps as small as dust motes-might be deployed to collect and process a rich array of information about enemy movements, crop conditions, pollution or anything else requiring monitoring. Realizing such a vision will demand advances in everything from microscale sensors to materials to programming. It's a huge undertaking. But there's a common benefactor: the U.S. Defense Advanced Research Projects Agency, which brokered the desert experiment and is funding ambitious investigations into each of the technologies involved.

Commonly known as DARPA, this is the U.S. Department of Defense's storied outpost of technology research-military systems, yes, but also innovations that sometimes create and transform industries. Formed in 1958, in the technological frenzy sparked by the Soviet Union's launch of its Sputnik satellite, DARPA boasts a four-decade-long history of promoting novel technologies-today doling out nearly $2 billion annually to corporate, government and university researchers in support of high-risk, potentially high-impact ideas. Among its many successes (see "Four Decades of Success," p. 45), DARPA's gambles proved instrumental in spawning the Internet and the computer mouse, stealth aircraft and the chip that makes your cell phone work-advances that meant research as out-of-the-box in its time as dust-mote-sized sensors seem today.