This project investigates microemulsions; the objective of the research is to improve on the understanding of phase transitions, microstructures, bulk, and interfacial properties and interactions in microemulsions. Pure component systems containing non-tonic, ionic, and zwitterionic surfactants will be investigated using a battery of analytic tools. Techniques to be used include dynamic light scattering and electrochemical methods for diffusion coefficients and, hence, aggregate size, average intensity measurements for the virial coefficients and radius of gyration, electrophoretic light scattering for zeta potential in charge systems, and surface light scattering for interfacial tensions. These measurements will be complemented with necessary phase behavior and analytical studies. The effects of composition, temperature, and pressure will be determined, and correlations will be developed to model the behavior.