The Lab Experiment That Saved Millions of Lives

A long time ago, doctors did not understand why some blood transfusions failed.

Many patients died after receiving blood from another person.

A scientist named Karl Landsteiner wanted to find out why this happened.

In 1900, he started a very important experiment in his laboratory.

He took blood samples from himself and his coworkers to study them.

Landsteiner mixed the different blood samples together carefully.

He noticed that some blood cells clumped together in the test tubes.

Other blood samples mixed perfectly without any visible problems.

This clumping was actually a reaction from the immune system.

He realized that human blood is not the same for everyone.

Landsteiner identified three main groups at first: A, B, and C.

Later, the C group was renamed to group O.

This discovery explained why some transfusions were very dangerous.

Doctors could finally match donors with the right patients safely.

Landsteiner received a Nobel Prize for this incredible work in 1930.