We take about six months to create our annual list of the most impressive young scientists in the U.S., six months of quizzing academic department heads, professional organizations and journal editors about the most creative and important research in the country and the individuals making it happen. And every year, those leaders-a serious and measured group-nominate hundreds of candidates with barely contained excitement. "There is no doubt in my mind that his work will revolutionize the field," says one. "He has done something that, frankly, I thought was impossible," says another.