James Daniel Hardy was a surgeon and researcher practicing in the United States during the twentieth century who studied organ transplantation, or the transfer of an organ from a donor to another individual. In 1963, he performed one of the first recorded lung transplants from a human lung donor. The transplant was successful for three weeks before the patient died of kidney failure. In 1964, Hardy also performed one of the first human heart transplants with a chimpanzee donor, and the transplanted heart pulsed for ninety minutes in the patient’s chest prior to death. He also collaborated on one of the first successful uterus and ovary transplants in a dog, in 1966. Hardy’s research on organ transplantation helped paved the way for improved forms of the technique, which as of 2025 saves the lives of millions of people every year.

Étienne-Louis Arthur Fallot was a physician working in France during the late nineteenth century who studied and described the four cardiac anatomical defects that cause the congenital anomaly known as the Tetralogy of Fallot. Those four heart defects result in deoxygenated blood recirculating through the body, giving the skin a blue-like color, a process called cyanosis. Numerous physicians and researchers before Fallot had identified and described the anatomical cardiac defects that would eventually be included in the Tetralogy. However, Fallot was among the first to note that the four anatomical heart defects tended to occur together. Through autopsy investigations, Fallot established the Tetralogy as one unified pathology rather than four unrelated anatomical abnormalities, providing a basis for the eventual surgical treatment of the condition, which affects approximately four out of every one thousand births worldwide.