Paul Ehrlich was a German physician and scientist who worked in the fields of hematology, immunology, and chemotherapy. He invented the precursor technique to Gram staining bacteria, and the methods he developed for staining tissue made it possible to distinguish between different type of blood cells, which led to the capability to diagnose numerous blood diseases. His laboratory discovered Arsphenamine, the first effective medicinal treatment for syphilis, thereby initiating and also naming the concept of chemotherapy. Ehrlich popularized the concept of a “magic bullet”. He also made a decisive contribution to the development of an antiserum to combat diphtheria and conceived a methodology for standardizing therapeutic serums. In 1908 he received a Nobel Prize in Physiology or Medicine for his contributions to immunology.