The physiology of red blood cells was the primary objective today. The function of carrying oxygen on hemoglobin molecules, the chemistry of the hemoglobin, the importance of iron in the molecular structure and that 300 million molecules of hemoglobin are found on each red blood cell, with each hemoglobin carrying 4 oxygen molecules, results in a massive amount of oxygen carried to the body cells. The recycling of the iron and cell parts by the liver, after the blood cells have been destroyed by macrophages shows how nature acts.