The topics falling under the heading biological calcification are exceedingly numerous and varied. They include systems as different as vertebrate skeletons and mollusks, in vitro cultures and unicellular organisms, ectopic calcification and urinary stones. Furthermore, the results are scattered through a huge number of scientific publications. Although calcification is probably one of the most widespread biological processes, the mechanisms which lead to calcification of biological systems are still unexplained. For the first time, this book offers a critical review of the calcification process, of the organic and inorganic phases of mineralized tissues, focusing on the earliest phases. It includes a methodological chapter which provides the necessary practical information for making appropriate choices. By collecting results from as many different sources as possible, and on the basis of personal experience, an integrative approach to a unified theory of this biological mechanism is given.