Pluripotent cells of the early embryo originate all types of somatic cells and germ cells of adult organism. Pluripotent stems cell lines were derived from mammalian embryos and adult tissues using different techniques and from different sources. Despite different origin, all pluripotent stem cell lines demonstrate considerable similarity of the major biological properties. This book examines the fundamental mechanisms which regulate normal development of pluripotent cells into different lineages and are disrupted in cancer initiating cells. Analysis gene expression profiles, differentiation potentials and cell cycle of normal and mutant pluripotent stem cells provide new data to search molecular targets to eliminate malignant cells in tumors. In this book, the authors also aim to present a global picture of how extracellular signals, intracellular signal transduction pathways and transcriptional networks cooperate together to determine the cell fate of pluripotent stem cells. Practical, ethical and legal considerations that must be addressed before induced pluripotent stem (iPS) cells can realize their potential in the treatment of degenerative disease is discussed as well. Recent advancements in the cancer stem cell hypothesis are also summarized and the challenges associated with targeting resistant cancers in the context of stem cell microenvironments are presented.