People have been cutting up human bodies to discover their mysteries for thousands of years. However as Christianity swept across Europe about 1,500 years ago, dissection was outlawed in most Christian countries as the Church believed the body had to remain intact for the Day of Judgement. From the Medieval period, about 700 years ago, it became acceptable for surgeons to use the bodies of convicted criminals to study their anatomy. Today scientists use embryos, umbilical cords, bone marrow and blood to research the potential of stem cells (particular cells of the body that can divide and produce more specialised cells). This research is producing treatments for certain types of cancer, diabetes and Parkinson’s disease, and for regenerating damaged body parts such as the eyes or the liver.