It takes no time for Francis Collins, the director of the National Institutes of Health, to recall the moment when he knew he wanted to be a scientist. “Tenth-grade chemistry class,” he says over the phone from his home office in Chevy Chase, Md., where he has been working since most of the NIH campus in Bethesda, Md., shut down in March. Much of the science he had learned before then was “descriptive” and uninteresting, he explains—but for this class, students used experiments to figure things out. “It became clear to me that science is like a detective story,” says Dr. Collins, 70. “If you’re good at it, you’ll discover...