Hypothetical choices from FuturePundit: "Suppose you find a lamp that contains a genie. Suppose the genie grants you 3 wishes to make parts of your body young again. You have to use the wishes by age 55 (before most old age diseases become apparent) or immediately if you are already over 50. The wishes are for only parts of the body. Each could make an organ (and the skin is an organ) or subsystem (e.g. immune cells or spine) young again." This is something of a proxy for the question "what specific rejuvenation research would you fund if you had a vast sum of money?" Tissue engineering for a new heart, plus the necessary understanding to repair any damage in your stem cells? One problem you quickly run into in this sort of thought experiment is that everything of importance is influenced by everything else. New cells will be damaged by the old intracellular environment, as well as by the actions of old cells next door. An age-damaged immune system can't protect rejuvenated cells in a new heart. The interconnectedness of the body's systems is one of the reasons I favor the fundamental engineering approach: get to the bottom of the biochemical damage and fix it. Take care of the cells and the environment and the organs will take care of themselves.