Bone marrow transplantation is an organ transplant in the human body because a blood transfusion is the smallest organ transplant in the human body. As the mother cell of blood, the largest blood-producing organ in the body, bone marrow transplantation is an organ transplant, and it is a highly technical organ transplant. Because bone marrow needs to be matched, an incompatible match may result in severe rejection leading to organ transplant failure or severe rejection leading to the patient’s death. In general, bone marrow transplants are used to treat leukemia or to treat serious hematologic disorders.