Microemulsions are stable, transparent solutions of water, oil, and surfactant, either with or without a cosurfactant. Microemulsions have been described as consisting of spherical droplets of a disperse phase separated from a continuous phase by a fi lm of surfactant [1-4] and they are highly dynamic structures. The components organize themselves in time and space by means of different interactions or collisions, giving rise to coalescence and redispersion processes. Numerous studies have been carried out with the aim of determining the structure, dimensions, and internal dynamics of these systems. Among these studies we can

cite those involving ultrasedimentation [5], different dispersion techniques [6], time-resolved fl uorescence [7], and nuclear magnetic resonance [8]. As these systems provide both organic and aqueous environments, microemulsions can simultaneously dissolve both hydrophobic and hydrophilic compounds, with each compound distributed between water, organic solvent, and surfactant fi lm in accordance with its physicochemical properties. Due to their microheterogeneous structure, microemulsions have found a growing number of scientifi c and technological applications: they afford control over the size of synthesized microparticles [9] and they have numerous applications in the fi elds of solubilization and extraction [10-13]. Microemulsions have also been used to simulate complex biological structures [14-19] (particularly in terms of the behavior of trapped water). In keeping with this ever-expanding range of applications, there is an increasing interest in studying the details of chemical [1], photochemical [20], and enzymocatalytic [1,21,22] processes in microemulsions. In particular, microemulsions-like phase transfer catalysis systems-are able to enhance reactions between nonhydrosoluble organic substrates and hydrosoluble reagents and, as a result, the kinetics of numerous reactions in microemulsions have been studied [2,23-31].