1)Example, Whole-body transplant, or brain transplant: (moves the brain of one being into the body of another) "The necessary technology currently does not exist to fully and safely perform this procedure. However, other technologies, such as human cloning, seemed equally impossible a generation ago." http://en.wikipedia.org/wiki/Whole-body_transplant 2) Example, Head transplant: (a surgical operation involving the replacement of an organism's head with a replacement head.Head transplantation invariably involves decapitating the patient.) "Ethical considerations have thus far prevented any reported attempt by surgeons to transplant a human being's head." http://en.wikipedia.org/wiki/Head_transplant 3) "Rejection and the side effects of preventing rejection (especially infection and nephropathy) were, are, and may always be the key problem." http://en.wikipedia.org/wiki/Organ_transplant 4)We do not do some type of transplants, because we do not have at the present time the technology to establish all the connections. Here you can find a timeline of succesful transplants. http://en.wikipedia.org/wiki/Organ_transplant#Timeline_of_successful_transplants