A remarkable paradigm shift has occurred in recent years regarding the biological origins of cancer. The cancer stem cell hypothesis challenged the foundational notions of cancer, and the therapeutic implications have been profound. Compelling evidence indicates that errors in the development of a small subset of adult stem cells can lead to cancer. Only this small sub-population of cells has the inherent ability to form tumours and metastasize. This book discusses the emerging field of cancer stem cell research, with contributions from leading experts on the basic biology, genetic pathways, and potentials for therapeutic targeting of cancer stem cells. It also covers clinical challenges for these new discoveries, namely, that cancer stem cells might be resistant to conventional chemotherapeutic and radiological treatments and may be at the biological core of relapse and therapeutic resistance. This book is an essential concise guide to the latest discoveries and therapies in cancer research.