Stem cells are important to medicine for their potential as all-purpose tools for restoring health in patients who need organ or tissue repair. Stem cells are naturally used by adult bodies to grow fresh tissue at sites of infection or damage.
Stem cells are what researchers call "totipotent," which means they are able to reproduce into cells of every type the body uses. During embryological development, stem cells are the key to growing the various tissues and structures of the body, and they remain active in growing new tissue throughout childhood. In adults, stem cells provide a continuing supply of fresh cells for tissue that wears down or becomes infected.
Stem cells have shown great promise in laboratory settings to address many of the most serious medical needs people have. Stem cell therapy holds the potential to produce an unlimited supply of rejection-free replacement organs for patients with heart disease or certain types of cancer, such as leukemia. More optimistic projections of stem cells' potential involve possibly regrowing missing digits or even whole limbs, reconnecting the spinal cords of paralyzed people and restoring virtually every organ system in the body to full health in the event of a catastrophic illness.