The blood revolution initiated by the famous footnote of Karl Landsteiner's 1900 paper.

A 1900 publication authored by Karl Landsteiner, at the age of 32 years, contained a footnote which stated that, "the serum of healthy human beings not only agglutinates animal red cells, but also often those of human origin, from other individuals". He followed up this statement in his 1901 paper, and concluded that, "My observations reveal characteristic differences between blood serum and red blood cells of various apparently healthy persons" and that "the reported observations may assist in the explanation of various consequences of therapeutical blood transfusions". These significant observations resulted in the discovery of A, B, O and AB blood groups and later led to successful blood transfusions in humans. The impact of the revolutionary finding by Landsteiner also changed a number of biomedical disciplines such as immunochemistry, medical anthropology, forensic medicine, genetics and pathology.