Xenotransplantation, the practice of transplanting an organ from a non-human animal, such as a pig or chimpanzee, to a human, has its origins in the 1960s. Among six patients receiving kidney xenotransplants from chimpanzees in 1963, one survived for nine months in moderate health. So far, the field has yet to overcome the problem of rejection of transplanted tissues by the immune system. However, with multiplex editing or genome writing, genetically engineered organs from pigs that resist rejection may revolutionize medicine. In this clip, Dr. George Church discusses how engineering animal organs may make them suitable for human transplant.