The idea:An online marketplace for laboratory researchers to exchange everything from leftover chemicals to unused microscopes

The aha moment:Three years ago, Garry Cooper, then a neurophysiology postdoc at Northwestern University’s Feinberg School of Medicine, was helping clean out a lab freezer when a colleague started to toss several vials of antibodies into the trash. “I said, ‘Hey, let me see if some other researchers could use those,’ ” he says, “and I found one who could. I realized there was a much broader application for this idea.”

Since then:Rheaply—the name is a mash-up of “research” and “cheaply”—has become a go-to buy-sell-trade group for Chicago’s scientific set. A year after his freezer-side epiphany, Cooper, 34, and cofounder Tyler Skelton left their day jobs (Cooper had become a consultant at Ernst & Young; Skelton was a designer at Guaranteed Rate) to launch the site, which works like online classifieds. Organizations pay a sliding subscription fee, which allows their lab workers to post castoffs and browse for supplies, many free or at a steep discount. One person’s trash is another’s ultraniche treasure: A Rheaply user recently sold a rotary evaporator, a device that helps purify samples, for less than $3,000. Its cost new? Up to $7,000. Rheaply has partnered with Northwestern and is close to finalizing deals with the University of Illinois at Chicago, Rush University, and even the National Institutes of Health. “We see ourselves building the Amazon.com for the scientific research world,” Cooper says.