This scientist has saved one BILLION lives!

This scientist Karl Landsteiner discovered that different people's blood had different characteristics that made it "incompatible" with other people's blood that didn't carry those same traits. He discovered the A, B, and O blood types. His discovery of the differences and identification of the groups that were alike made it possible for blood transfusions to become a routine procedure. This paved the way for many other medical procedures that we don't even think twice about today, such as surgery, blood banks, and transplants.
Over 1 Billion Lives Saved So Far!
Source:  HERE

Karl Landsteiner
 (June 14, 1868 - June 26, 1943)