Each blood type is also grouped by its Rhesus factor, or Rh factor. Rhesus refers to another type of antigen, or protein, on the surface of red blood cells. The name Rhesus comes from Rhesus monkeys, in which the protein was discovered. Blood Transfusions Blood types become very important when a blood transfusion is necessary. If the blood types are not compatible, red blood cells will clump together, making clots that can block blood vessels and cause death.
Blood type is inherited, just like eye color.
Certain blood types are more common in certain countries. Different kinds of animals have different kinds of blood. Some people think blood type tells about personality.