Alexandra RadulovichKarl Landsteiner (June 14, 1868 – June 26, 1943) was an Austrian pathologist/immunologist responsible for the discovery of the different blood groups in humans and ABO. classification system in 1901; a discovery that earned him the Nobel Prize in Physiology or Medicine 30 years later. At the age of seventeen, Landsteiner was admitted to the medical faculty of the University of Vienna where his interest in chemistry grew and he adopted the method of approaching medical anonymities through the lens of a chemist . Always attracted to research, Landsteiner conducted studies on the influence of diet on blood composition, publishing one of his first articles while he was still a student. Having an affinity for the nature of antibodies and the mechanisms associated with immunity, Landsteiner's experimental trials were conducted with the aim of understanding the reason underlying the fatal outcome of blood transfusions in patients. He suggested that the cause of clotting could be attributed to the presence of agglutinogens (antigens) which he named A and B, which...