The document describes 8 steps in the development of blood cells: 1) stem cells differentiate into progenitor cells, 2) progenitor cells further differentiate, 3) cells continue to mature, 4) at step 4 cells become either lymphocytes, monocytes, or granulocytes, 5) cells further mature and develop specific blood cell features, 6) maturation continues as cells prepare to enter circulation, 7) maturation is nearly complete, 8) fully mature blood cells enter circulation.