A greater knowledge of the physical and chemical properties of microemulsions is important to future scientific and industrial applications of new microemulsions, as well as for improvements as drug delivery system with currently available microemulsions. This thesis are attempt to study the microemulsions with two basic objectives: (I) to determine the effect of each constituent solubilized in ME on droplet size and stability, (II) to examine the physical basis of the interactions between the microemulsion droplets. The experimental approach has been based upon the use of three different scattering techniques, SLS, DLS and SANS. The combination of these scattering techniques is found an excellent one for the characterization of microemulsions unambigously. Diffusion dynamics and interdroplet interaction of Water/AOT/n-alkanes microemulsions in the large concentration range are studied for the first time, along with the droplet size growth, shape and size fluctuation of microemulsion droplets using contrast variation experiments. Self-consistent results are obtained for size, size polydispersity and interdroplet interaction of microemulsions droplets from three different scattering techniques. The results obtained from Water/AOT/n-alkanes systems are directly applied to examine the physical basis of the interdroplet interaction and behavior of each constituent solubilized in complicated microemulsions of pharmaceutical interests.