The present book consists of contributions, which have been presented and discussed in detail in the course of the research workshops Nucleation Theory and Applications organized jointly by scientists from the Bogoliubov Laboratory of Theoretical Physics of the Joint Institute for Nuclear Research in Dubna, Russia, and the Department of Physics of the University of Rostock, Germany, involving colleagues from Russia, Belorussia, Ukraine, Kazakhstan, Estonia, Bulgaria, Czech Republic, Brazil, United States, and Germany. These workshops have been conducted yearly for about one month in Dubna, Russia, starting in 1997. The intention of these workshops was and is to unite research activities aimed at a proper understanding of both fundamental problems and a variety of applications of the theory of first-order and second-order phase transitions, in particular, and of the typical features of processes of selforganization of matter, in general. The meetings in Dubna have been supplemented hereby by mutual research visits of the participants in the course of the year in order to continue and extend the work performed during the workshops.