Bone marrow is a blood-rich soft connective tissue found in the cancellous space of the bone and the cavity of the long bone marrow, which is divided into red and yellow marrow in the human body. The main function of red bone marrow is hematopoiesis, as well as defense, immunity, wound repair, and promotion of bone healing and defect repair. The yellow bone marrow is filled with fatty tissue and has no hematopoietic function, and its main function is to nourish bone. In normal adults, the ratio of red marrow to yellow marrow is 50/50, but as people age, the red marrow gradually decreases and the yellow marrow gradually increases. However, in cases of severe anemia or hemorrhage, yellow marrow can be converted to red marrow to continue blood production.