With the company's name and logo taped to the glass door, the unpacked boxes, an empty reception desk, and young scientists bustling about, it could be any Silicon Valley company in the chaos of starting up. But this, it quickly becomes apparent, is not an ordinary startup. You begin to notice the difference a few doors past the coffee maker. Just down the hall, in a windowless room lit by the faint glow of a green laser shooting through a maze of optical equipment, you'll find the company's crown jewels, tiny particles emitting a variety of colors. These are quantum dots-crystals made up of only a few hundred atoms. Viewed through an ordinary optical microscope, they twinkle like stars in a moonless sky.

Quantum Dot Corporation-and its handful of high-profile venture capital investors-is betting these glowing specks will change how biologists view the cellular world. The particles measure only a few nanometers (billionths of a meter) across. Because this is about the same size as a protein molecule or a short sequence of DNA, quantum dots could be near-perfect beacons for lighting up biological events. They come in a nearly unlimited palette of colors and can be linked to biomolecules to form sensitive probes to identify specific compounds and track biological events.