Matt Bell was a Stanford University undergraduate in 2001 when he started tinkering with what would become the basis for his company, Reactrix Systems. "I created this program for people to play with flames projected on a wall. I thought it might be good for raves," recalls the now 25-year-old Bell. The project might have retained its digital-toy status were it not for a trip Bell took to London that spring. "I saw ads projected onto the street," he says, "and thought, 'Wouldn't it be neat if I could "play" with the ad I just walked through?'"

So Bell decided to leave his job at Google and, along with fellow twenty-somethings Jon Friedberg and Mike Schaiman, raise $400,000 to launch Reactrix, a company specializing in "immersive interactive displays." By the end of 2002, the company had its first commercial deployment, an interactive floor at Toys R Us that let children chase the company's star-shaped logo; each time a kid stepped on a logo it would "pop" and transform into the store's mascot, Geoffrey the giraffe. This was soon followed by an installation at Las Vegas nightclub Tabu that let people dance with images projected onto tables.