The longest lived laboratory animals shed light on the forces that lead some to any early grave and others to beat the odds and see many more birthdays than the norm. Experiments with mice, flies, and worms have won that manipulating genes, restricting calorie intake, and giving animals drugs can extend life span—by as much as 10-fold. Researchers also have elucidated several biochemical pathways that lead to longevity. And one lab animal, the hydra, appears to have found a fountain of youth of sorts: Unless it sexually reproduces, it appears immortal.