This book focuses on mesenchymal stem cells (MSCs) of animal origin, including their isolation, characterization, and clinical applications. After briefly discussing the historical development of the field of stem cell research, it describes the basic properties and nature of stem cells particularly in relation to MSCs. In turn, it reviews materials and methods used to isolate MSCs from various sources, culture expansion, characterization and long-term storage. It also explores the therapeutic efficacy, immunomodulation and anti-inflammatory, and differentiation properties of MSCs. Importantly, the book discusses the applications of genetic engineering to enhance the efficacy and potential of MSCs in regenerative medicine. The book largely addresses the potential applications of mesenchymal stem cells in therapies for important species of domesticated animals including sheep, goats, cattle, buffalo, cats, dogs and horses. Finally, the book presents an abridgement of challenges and future prospects of stem cell research and application in medicine, in general and veterinary sciences, in particular.