Konrad Hochedlinger, 32

In 2006, scientists demonstrated that inserting four embryonic genes into mouse skin cells induced a small fraction of them to look and behave like embryonic stem cells. The technique promised to eliminate the need to destroy embryos to generate stem cells. But the first cells made this way were not completely "reprogrammed."

Konrad Hochedlinger, an assistant professor of medicine, found a simple way to improve the technique. Working with mouse cells, he initiated the reprogramming process by means of the same four genes that previous scientists had used. But he used a different gene to identify the cells that had been successfully reprogrammed; cells in which that gene is active turn out to look and act more like embryonic stem cells than those made previously. The technique offers a way around the controversies that have slowed embryonic-stem-cell research, which has the potential to help scientists understand certain diseases and, eventually, replace diseased or damaged tissue. --Emily Singer