Stem cells (unspecialized cells) have the ability to self-replicate and transform into an array of specialized cells. These cells have two unique properties: self-renewal capacity and the ability to undergo differentiation pathways or enter terminal divisions to yield an organized tissues or functional blood cells. Both embryonic and adult stem cells, therefore, can be used to generate healthy tissues and replace the damaged ones. For instance, they can be used to produce insulin-secreting cells for the treatment of type I diabetes, to generate liver cells for patients with liver failure, to treat neurodegenerative disorders like Alzheimer's and Parkinson's disease, to cure myocardial infarction, etc. Thus, we envisage a possibility to restore normal functions with the application of stem cells. Stem cell research focuses on the potential applications of stem cells. This advancing field of science is making possible cell-based therapies to treat a myriad of diseases. In the present book, we focus on stem cells and their applications. This book will be useful for students who are interested in the area of regenerative medicine, health sciences and biotechnology.