On August 9, 2001, Mathew "Willy" Lensch sat with his wife in their Oregon living room and watched President George W. Bush speak to the nation. Millions of Americans had their TVs on, but unlike most of them, Lensch was, as he puts it, "on the edge of my chair, the rest of the universe ceasing to exist."

Lensch was finishing his PhD in molecular and medical genetics. His research specialty was a genetic malady called Fanconi anemia, which often kills its victims before they reach adolescence. The disease is caused by the malfunctioning of special cells in the bone marrow: stem cells, the precursor cells that create and maintain the body's supply of blood cells. Fanconi victims' best hope for a cure, Lensch believed, lay in re-creating their missing blood cells from embryonic stem cells -- stem cells derived from an early human embryo, which are unusually adaptable and changeable. Earlier that year, Lensch had accepted a position with a brand-new stem cell group that is now based at Children's Hospital Boston, a prominent biomedical research center.