Transplant surgery has now reached incredible heights, from achieving full face transplants to growing organs in the lab. This Horizon Guide looks back at the extraordinary odds doctors and patients have had to overcome to achieve these amazing breakthroughs. What we now take for granted has been a hard won struggle, both for the patients who were willing to gamble their lives and the doctors who faced ethical and medical dilemmas in the name of progress. Michael Mosley looks through the Horizon archive, identifying the key turning points for transplant surgery to explore how far science can go in its bid to prolong life.