Illustration of hematopoesis, a physiological process that allows the formation and renewal of blood cells. The stem cells come from red bone marrow of flat, short bones shown in pelvic bones in the illustration. These stem cells produce two types of cell : - Myeloid stem cells which form red corpuscles, platelets and white corpuscles (polynuclear and monocytes). - Lymphoid stem cells, which form white corpuscles (lymphocytes).