Dr. John Gibbon performed the first successful open-heart surgery using a heart-lung machine he spent 20 years developing. The machine temporarily takes over the function of the heart and lungs, oxygenating the blood and pumping it through the body so the heart can be stopped and operated on in a dry, still environment. Before this, heart surgery was virtually impossible. This invention paved the way for bypass surgeries, heart valve replacements, and organ transplants. It is one of the most significant advances in surgical history, turning once-fatal cardiac defects into treatable conditions.