Karl Landsteiner (1868-1943) was an Austrian scientist of Jewish descent. He is a figure who discovered that human blood is divided into 4 groups now known as blood groups O, A, B, and AB. With this discovery, people can transfuse blood safely and not carelessly.
Landsteiner is a doctor who plays an integral role in the identification of blood types. He demonstrated the effects of disasters that occur if one transfuses blood types, and shows the hereditary nature of the blood type, which has since been used as a method of showing offspring.
Landsteiner also played a role in the identification of the polio virus, and gave many contributions to immunology, histology, and anatomy. The biggest legacy of his knowledge is understanding different blood groups for blood transfusions, which play an important role in increasing survival in surgery.