In 1954, Joseph Murray attempted a type of kidney swap that no doctor had tried before. The surgery was a success, and the patient would go on to live with the transplanted organ thanks to one key factor: it came from his identical twin. 70 years later, nearly 100,000 kidneys are transplanted annually in the US alone. So how does this surgery work today? Alexander H. Toledo explains the procedure. Lesson by Alexander H. Toledo, directed by Biljana Labović.