All blood cells are the progeny of hematopoietic stem cell. Differentiation and maturation of hematopoietic cells is regulated by endogenously produced cytokines like erythropoietin, granulocyte colony stimulating factor and granulocyte macrocyte colony stimulating factor. The process by which red cells, white blood cells and platelets are produced in bone marrow is termed as erythropoiesis, myelopoiesis and megakaryopoiesis respectively. All these processes start with the stem cell progeny and after passing through different stages of maturation end with mature circulatory RBC, WBC or platelets.