America's Best

So to select the best in science and medicine today, we focused on the most exciting fields of research and then looked for the men and women who are doing the most cutting-edge work within those fields. Along the way we learned that at least one thing hasn't changed: what it takes to be great in science or medicine. Although few researchers work alone anymore, and most have to spend at least part of their day worrying about how to keep large quantities of cash flowing into their labs, the greatest breakthroughs still come from brilliant individuals with a passion for understanding the world and the ability to concentrate obsessively on a problem until they have solved it. Here are 18 at the forefront of asking the crucial questions and finding the breathtaking answers.