Much of our knowledge of stem cells has been inferred from studies of remarkable few species. The ability to manipulate stem cells in "model" organisms such as the mouse and a few other vertebrate species has driven our understanding of basic biology of stem cells. The power and efficiency of studying model organisms, however, comes at a cost since a few species, obviously, do not reflect nature´s true diversity. Unfortunately, although all multicellular organisms seem to rely on stem cells, and although this seems to be a question of key importance for understanding the evolution of animal life, little is known about stem cells in early-branching taxa. "Stem Cells: From Hydra to Man" illustrates that there is more than human and mouse stem cells to learn from. Reflecting an enormous growth in the knowledge of stem cells in various organisms, the book presents the conceptual language and the nature of questions, as well as a summary of the advances in our understanding of stem cells from a comparative point of view that has resulted from the development of new technology and the development of novel model organisms over the past few decades. As such this book is largely a horizon analysis of a frontier rather than a retrospective. It presents an integrative approach to animal stem cells and covers the major contributions, tools and trends in a newly emerging field: comparative stem cell biology.

1. Plant Stem Cells: Divide et Impera, Jan U. Lohmann; 2. Stem Cell System of Sponge, Noriko Funayama; 3. Stem Cells in Immortal Hydra, Thomas C.G. Bosch; 4. Stem cells in planarian, Kiokazu Agata; 5. The Stem Cell System of the Basal Flatworm Macrostomum lignano, Peter Ladurner, Berngard Egger, Katrien De Mulder, Daniela Pfister, Georg Kuales, Will Salvenmoser, and Lukas Schärer; 6. Regeneration and Stem Cells in Ascidians, Stefano Tiozzo, Federico D. Brown, and Anthony William De Tomaso; 7. In vitro Control of Organogenesis by ActivinA Treatment of Amphibian and Mouse Stem Cells, Makoto Asashima, Akira Kurisaki, and Tatsuo Michiue; 8. Melanocyte stem cells: an excellent model to study stem cell biology, Masatake Osawa, Kiyotaka Hasegawa, Mariko Moriyama, and Shin-Ichi-Nishikawa; 9. In vitro hESC Technology: State of the Art and Future Perspectives, William Lathrop Rust; 10. Tumor Stem Cells: How to Define Them and How to Find Them? Ibrahim Alkatout and Holger Kalthoff; Subject Index.