The development of new biomedical technologies has some enthusiastic proponents -- scientists, the medical community, patient organisations, and politicians all hope for new cures and new industrial applications. At the same time, there is resistance to the new technologies from other groups for a variety of religious, political, and ethical reasons. In this book, Anders Persson and Stellan Welin address the important perspectives on xenotransplantation and human embryonic stem cell research. For various reasons, the methods have been fervently promoted and equally vehemently opposed by different groupings. The authors investigate the political, social, and ethical forces at work, and discuss how this kind of research and development is affected by the necessary involvement of commercial actors and strong financial incentives. Stories of hope, fear, and hype are matched by stories of success, failure, and fraud. Xenotransplantation and the use of human embryonic stem cells are truly contested technologies.