Stem cells are undifferentiated biological cells that can differentiate into specialized cells and can divide (through mitosis) to produce more stem cells. They are found in multi-cellular organisms. In mammals, there are two broad types of stem cells: embryonic stem cells, which are isolated from the inner cell mass of blastocysts, and adult stem cells, which are found in various tissues. In adult organisms, stem cells and progenitor cells act as a repair system for the body, replenishing adult tissues. In a developing embryo, stem cells can differentiate into all the specialized cells—ectoderm, endoderm and mesoderm—but also maintain the normal turnover of regenerative organs, such as blood, skin, or intestinal tissues. Adult stem cells are frequently used in various medical therapies (e.g., bone marrow transplantation). Stem cells can now be artificially grown and transformed into specialized cell types with characteristics consistent with cells of various tissues such as muscles or nerves.

In the present book, thirteen typical literatures about stem cell published on international authoritative journals were selected to introduce the worldwide newest progress, which contains reviews or original researches on medical science, biotechnology, cell biology, cytology, ect. We hope this book can demonstrate advances in stem cell as well as give references to the researchers, students and other related people.