An overview of recent developments in the field of first-order phase transitions, which may be considered a continuation of the previous work 'Aggregation Phenomena in Complex Systems', covering work done and discussed since then. Each chapter features a different aspect of the field written by international specialists, and covers such topics as nucleation and crystallization kinetic of silicate glasses, nucleation in concentration gradients, the determination of coefficients of emission of nucleation theory, diamonds from vitreous carbon.