In the last few years, multiscale methods have lead to spectacular progress in our understanding of complex physical systems and have stimulated the development of very refined mathematical techniques. At the same time on the experimental side, equally spectacular progress has been made in developing experimental machinery and techniques to test the foundations of quantum mechanics. In view of this progress, this volume is very timely; it is the first text totally devoted to multiscale methods as applied to various areas of physics and to the relative developments in mathematics. The book is aimed at mathematical physicists, theoretical physicists, applied mathematicians, and experimental physicists working in such areas as decoherence, quantum information, and quantum optics. Contributors: M. Arndt; J.E. Avron; D. Bambusi; D. Dürr; C. Fermanian Kammerer; P. Gerard; L. Hackermüller; K. Hornberger; G. Jona-Lasinio; A. Martin; G. Nenciu; F. Nier; R. Olkiewicz; G. Panati; M. Patel; C. Presilla; M. Pulvirenti; D. Robert; A. Sacchetti; V. Scarani; P. Stollmann; A. Teta; S. Teufel; C. Toninelli; and A. Zeilinger