Highs: Working in the promising and still-controversial field of stem cell research, Rossi discovered an innovative method for reprogramming skin cells back into stem cells. Until now, the creation of these so-called induced pluripotent stem (iPS) cells, which are derived from adult cells instead of embryos, has required the use of potential cancer-causing viruses and genes to help coax the adult cells back into an embryonic state. But Rossi's method bypasses that step, using messenger molecules — instead of the actual viruses or genes — to do the same work without the risks, such as cancer, that these elements pose. His new method could help move stem cell–based treatments for diseases such as diabetes and Parkinson's more quickly from the lab to the clinic.
Lows: It's still not clear that iPS cells like Rossi's are as useful as those that are derived from embryos — the gold standard of stem cell research — so work with embryonic stem cells must continue. In 2009, President Obama reversed a ban on federal funding for embryonic stem cell research, re-energizing the field. But last August those opposed to research on human embryos sued the government, threatening to put a halt to this work. An appeal has allowed federal grants in the field to continue while the suit is heard in court.
—Alice Park