Since the first successful isolation and cultivation of human embryonic stem cells at the University of Wisconsin - Madison in 1998, there have been high levels of both interest and controversy in this area of research. This book provides a concise overview of an exciting field, covering the characteristics of both human embryonic stem cells and pluripotent stem cells from other human cell lineages. The following chapters describe state-of-the-art differentiation and characterization of specific ectoderm, mesoderm and endoderm-derived lineages from human embryonic stem cells, emphasizing how these can be used to study human developmental mechanisms. A further chapter discusses genetic manipulation of human ES cells. The concluding section covers therapeutic applications of human ES cells, as well as addresses the ethical and legal issues that this research has raised.