Hematopoiesis begins with the pluripotent stem cell in the marrow and culminates in mature, functional red blood cells, white blood cells, and platelets in the circulation. The process consists of a complex and well‐orchestrated sequence of cell proliferation, differentiation, and maturation, that is stimulated and regulated by a host of cytokines and hormones. The various growth factors act individually and in concert at different stages of hematopoiesis and have important effects on mature cell functio