Marrow is a substance found in the cavities of the body's bones.
It resembles blood and contains stem cells, which produce red cells, white cells and other blood components. Bone marrow is a soft, fatty tissue inside the hollow bones of the hips, legs, and arms that is the site of blood production in the body. Approximately 75 percent of all transplants facilitated are for patients who have been diagnosed with some form of leukaemia. In addition, marrow transplants are a treatment for patients with anemias, lymphomas and a number of other life-threatening blood diseases. On most cells of the body, there are protein molecules called antigens that mark the cells.