Who was the first to classify the human blood group systems on the form which is now widely accepted in the medical practice internationally?

The Austrian-born American biologist Karl Landsteiner in 1901 was the first to classify the human blood group system-ABO BLOOD GROUPS. The method of classifying the human blood on the basis of the inherited properties of red blood cells (Erythrocytes) as determined by their possession of or lack of the so-called antigens A (including A, and A) and B. Persons may thus have type A, type B, type O or type AB blood. Antigens of other blood group systems may also be present.