An Italian version of this book has been published in 2009 by ENEA (The Italian Agency for New Technology, Energy and the Economic Sustainable Development) as a contribution to the International Year of Biodiversity. The book would like to be a response to the continuing request of information on the subject the authors receive from a variety of colleagues, administrators, politicians, journalists, stake-holders, students, even interested citizens. Such a request is a clear symptom of the increasing attention toward biodiversity, but also of the scarcity of information characterizing the matter. Particularly stimulating has been the curiosity and the inquisitiveness expressed by scientists and scholars active in fields other than biological diversity or ecology. The book is based on the authors international experiences and “pathways” within biodiversity, and wants to be informative, comprehensive, understandable, balanced and, at the same time, scientifically correct. A key idea has been to focus not only on conservation, but especially on sustainable use and consequent development. The book has been widely appreciated in Italy for its agility, information content, conciseness, and the attempt to conjugate scientific aspects with social, economic, and policy issues. In this context, it has been suggested to the authors to make available the book in the English language. However, the volume has been not only translated but also in good part re-written, to deal adequately with regional and international aspects, with particular attention to Mediterranean biodiversity in the countries of the Mediterranean Basis and of the other Mediterranean- type regions. The content embraces, in slightly over 200 pages, an introductory part on biodiversity, the description of the international actions, the discussion of problems of biodiversity management, some aspects analyzed under a magnifying glass (including Mediterranean biodiversity), a glossary, a bibliography, the text of the Convention on Biological Diversity, and a series of sketches of some (past and present) personalities of the biodiversity field.