This important and timely book deals with the theoretical and experimental investigation of the phase transitions which occur in complex fluid systems, namely lyotropic systems, microemulsions, colloids, gels, polymers, biological membranes, Langmuir monolayers, and ferrofluids. It contains 20-odd review papers from the major contributors to this rapidly growing field of research, summarizing the main results obtained in the description and understanding of the phase transitions taking place between the isotopic, nematic, cholesteric, lamellar, hexagonal, and cubic mesophases of complex fluids.