Adult Stem Cells are present in your body from the day you are born and are naturally produced in your bone marrow. Stem cells can become virtually any type of cell in your body. Without them, your body's natural  renewal process simply could not take place!
The Stem Cell Theory of Renewal proposes that stem cells are naturally released by the bone marrow and travel via the bloodstream toward tissues to promote the body’s natural process of renewal. When an organ is subjected to a process that requires renewal, such as the natural aging process, this organ releases compounds that trigger the release of stem cells from the bone marrow. The organ also releases compounds that attracts stem cells to this organ. The released stem cells then follow the concentration gradient of these compounds and leave the blood circulation to migrate to the organ where they proliferate and differentiate into cells of this organ, supporting the natural process of renewal.