Autologous stem cells can be harvested  from the bone marrow or circulating blood. This in turn can develop into mature cells if present in the right environtment within the body. Many of these cells are quite immature (multipotent), and they have the ability to develop or differentiate into a variety of more developed cell types. This includes the use of these multipotent cells to reconstitute bone marrow after high dose chemotherapy to treat various forms of cancer. Reconstitution of a more structurally complex organ than bone marrow poses a much greater challenge than simply administering stem cells into the circulating blood. Because of immaturity, these cells would need to be “programmed” to differentiate  along one particular pathway to help accomplish this assigned task. Their immaturity also poses the risk that cells could develop along unwanted pathway, including the development of disregulated cell growth, which leads to cancer.