Christiaan BARNARD was a South African cardiac surgeon who performed the world's first successful human-to-human heart transplant in 1967. He is best known for his pioneering work in the field of cardiac surgery, and his name is associated with the term 'heart transplant'. He also developed the technique of using a heart-lung machine to OPERATE on the heart, allowing surgeons to OPERATE on the heart without stopping it. His work revolutionized the field of cardiac surgery and has saved countless lives.