Bone marrow is a spongy, gelatinous, fat-containing tissue. It is mainly composed of blood vessels, nerves, reticular tissue and stromal cells, which are filled with hematopoietic cells. Normal human bone marrow accounts for 3.4% to 5.9% of body weight, with an average of 4.6%. Bone marrow is divided into red marrow (hematopoietic marrow) and yellow marrow (fat marrow). When a person is first born, the red marrow fills the bone cavity of the whole body, but as the person grows older, the red marrow gradually changes to yellow marrow, and this change starts from the distal end of the body in a centripetal development. Bone marrow regeneration is powerful and can compensate as soon as possible when the body needs blood cells quickly. So it is as a hematopoietic stem cell donor that can recover quickly after harvesting bone marrow or mobilized peripheral blood stem cells.