"I always wanted to be a pioneer," says molecular biologist Cynthia Kenyon, Ph.D. Casting about in the late 1980s for an understudied field to focus on, she found aging, which was then seen as simple decay. "People thought you just wore out, like an old car," recalls Kenyon, 53. "And I thought, 'No, there's going to be something beautiful here.'" The beauty Kenyon discovered is that aging can be turned on and off. In youth, a body's cells repair the small metabolic glitches that can occur as cells divide. But at a certain age that repair system slows down and mistakes accumulate, which causes symptoms of aging. Kenyon sought to delay the age at which that happens. Her breakthrough paper came in 1993: by tweaking a single gene in a one-millimeter worm, she had doubled its healthy life span. Because aging research was considered such a career killer at the time, Kenyon had difficulty enlisting grad students; now, students flock to her University of California, San Francisco, lab—and to the field—to build on her monumental work. One biographer likens Kenyon to the biblical Eve: the woman who brought knowledge to humankind. Kenyon's latest research links tumor growth to the aging process. Fiddle with worm genes to slow aging, and the side effect is resistance to cancer. Kenyon believes that future studies will show the same link to Parkinson's, Alzheimer's, and other diseases of aging: "The big, big, big payoff will be going after all the age-related diseases at once, just by going after the genes that control aging."