First Light: Homebuilt telescopes [foreground] atop Mauna Kea Courtesy Gaspar Bakos

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. Exclamation points abound.

So when we say that these 10 are the most creative, the most groundbreaking, the most brilliant, just what does it mean? It means they have the gall to ask the big questions, even if those happen to be outside the traditional areas of inquiry. It means they challenge what we thought it possible to know. It means their answers are opening up ever more perplexing questions.

And because of that, it means they still have a lot of work to do.