The current state of the art of various aspects of micro emulsion systems is reflected in this volume. Major topics discussed include: general background on solubilized systems, phase diagrams and phase equi- libria, bicontinuous microemulsions, Winsor's phases, theories and models of complex self association structures, cry tical behaviour, phase tran- sitions in lyotropic liquid crystals. I hope that this book will serve its intended objective of reflecting our current understanding of microemulsions both in theory and practice, and that it will be useful to researchers, both novices as well as experts, as a valuable reference source. I feel indebted to the people of the Ettore Majorana Centre: the friendly atmosphere of the Erice centre provided a very effective environ- ment to enjoy the company of colleagues and friends during breaks and after sessions, and to discuss problems of mutual interest. The courtesy, efficiency and devotion of the secretarial and technical staff was also appreciated, and greatly contributed to make the Workshop a smoothly run- ning one. The Scientific Secretary Donatella Senatra Department of Physics University of Florence (Italy) v INTRODUCTION The decision to publish. in a more permanent form than heretofore. the Proceedings of the Workshop on "Progress in Microemulsion" of the Inter- national School of Quantum Electronics. which was held in Erice (Italy) from October 26 to November 1st. 1985. under the auspices of the "Ettore Majorana" Centre for Scientific Culture. will prove to be a sound one.