The possibility of medicine to replace damaged organs in the body is making important headway. This programme reports on efforts to replace the most inaccessible organs with spare parts - the cochlea of a profoundly deaf two year-old and damaged retinal cells with light sensitive electronic chips are two case studies featured in the programme. The programme also examines how the body adapts to real life replacements instead of bionic substitutes in hand, limb and heart transplants and the issues surrounding the use of animal organs.