Blood Types
Each individual has a blood type. The method of knowing the blood types of humans was discovered by Karl Landsteiner in the early 1900s. He developed the ABO system, the most common blood type classification system. The four types of blood in the ABO system are, A, B, AB, and O.
Landsteiner observed two distinct chemical molecules present on the surface of the the RBCs. He named one molecule "A" and the other molecule "B".
Blood Type A
People with A blood type have A molecules on the surface of their RBCs.
Blood Type B
People with this blood type have B molecules on the surface of their RBCs.
