For centuries, people misunderstood how the heart works. As our knowledge grew, heart surgery remained a dangerous medical procedure. Even after organ transplants become common, surgeons struggled to transplant hearts and keep patients alive. But small groups of pioneering doctors attempted this difficult surgery, changing the lives of patients. This graphic history traces their leap forward and the medical world's newest advancements in heart-health technology. Learn about innovations such as artificial hearts and 3D printed living tissue.