Adult stem cells are undifferentiated cells found throughout the body that divide to replenish dying cells and regenerate damaged tissues. Also known as somatic stem cells, they can be found in children, as well as adults. Adult stem cells have been found in the brain, bone marrow, blood vessels, skeletal muscle, skin, teeth, heart, gut, liver, and other (although not all) organs and tissues. Although research into adult stem cells is promising, adult stem cells may not be as versatile and durable as are embryonic stem cells. Adult stem cells may not be able to be manipulated to produce all cell types, which limits how adult stem cells can be used to treat diseases.