This timely and topical book reviews the important development in the 'B 12-field' with regard to biological, chemical, pharmaceutical and medicinal aspects. In over 30 chapters the approx. 50 internationally renowned authors give deeper insight into the prospering research activities around B 12. Topics of particular interest include: - Biosynthesis of Vitamin B 12 - Structure and function of B 12-proteins - B 12-catalyzed enzymatic reactions and their mechanisms - Structural B 12-chemistry - Reactivity of B 12 and B 12-models - Metabolic transport and storage of B 12 - Pathological effects of B 12-deficiency