Stem cells have become icons of medical hope, and Sean J. Morrison has made fundamental discoveries that explain their workings. As a post- doc at Caltech, Morrison devised a way to harvest neural stem cells from fresh tissue rather than from tissue cultured in the lab, where stem cells might have been created as an artifact of the culturing process. In sodoing, Morrison clarified many of the cells’ properties. “He is one of the most talented stem cell researchers,” says David J. Anderson, Morrison’s advisor at Caltech. While studying similarities between stem cells and cancer cells, Morrison and a collaborator made the surprising discovery that tumor growth may be driven by rare “cancer stem cells.” Now an assistant professor at the University of Michigan, Morrison recently cofounded Cancer Stem Cell Genomics to investigate the possibility that that discovery could lead to better ways of developing cancer-killing drugs. The nascent company is Morrison’s second business foray. In college he developed an inexpensive process for mass-producing fungi, but his company lacked capital. Given stem cells’ medical applications, his new business is not likely to have similar trouble.