As new medical technologies are developed, more and more human tissues--such as skin, bones, heart valves, embryos, and stem cell lines--are stored and distributed for therapeutic and research purposes. The accelerating circulation of human tissue fragments raises profound social and ethical concerns related to who donates or sells bodily tissue, who receives it, and who profits--or does not--from the transaction. Catherine Waldby and Robert Mitchell survey the rapidly expanding economies of exchange in human tissue, explaining the complex questions raised and suggesting likely developments....