Dr. Willem J. Kolff invented the first artificial kidney, built the first artificial heart, and developed a membrane oxygenator. His kidney became the modern dialysis machine; his heart is still in use for patients awaiting transplants; and his oxygenator is used to keep people alive during open heart surgery. All told, his medical inventions have saved or extended countless lives. Born in the Netherlands, Dr. Kolff began working on the artificial kidney in 1938, but his research slowed down when the Nazis invaded the Netherlands in 1940. In order to avoid working with Nazi sympathizers, Dr. Kolff moved to a small town hospital that had fewer resources. While waiting there for the war to end, he set up the first blood bank in Europe and saved over 800 people from concentration camps by hiding them in the hospital. After the war, Dr. Kolff moved to America and worked in hospitals in Cleveland and Salt Lake City. He died on February 11, 2009, at the age of 97.