This volume looks at the state-of-the-science in stem cells, discusses the current challenges, and examines the new directions the field is taking. Dr. Turksen, editor-in-chief of the journal "Stem Cell Reviews and Reports," has assembled a volume of internationally-known scientists who cover topics that are both clinically and research-oriented. The contents range from sources of stem cells through their physiological role in health and disease, therapeutic applications in regenerative medicine, and ethics and society. An initial overview and a final summary bookend the contents into a cohesive and invaluable volume.