The body has an excellent capacity for self-renewal, but there are limits to its powers. Although lost skin can be regrown, a lost limb or organ cannot. If a person’s nervous system is damaged and they are paralyzed, there is no way to repair that damage. Furthermore, the ability of the body to regenerate itself decrease with age, leaving the elderly prone to death or suffering from stresses that would barely harm a younger person. Regenerative medicine focuses on repairing damage to the body that cannot be repaired by other means; stem cells are integral to this strategy, as their ability to be programmed into any type of cell makes them the ideal tool for rebuilding biological structures. Successful research into regenerative medicine would mean that there would be almost no type of injury that could not be repaired.