We have used the fluorescence probe Prodan to characterize the structure of reverse micelles formed in the ternary system of surfactant Aerosol OT, sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/heptane/water. Our results demonstrate that Prodan is a novel and powerful probe of the features of reverse micellar systems as a consequence of its solubility and measurable fluorescence intensity in a wide range of solvents of varying polarity. These characteristics govern the distribution of the probe into the microregions of the reverse micelle and yield fluorescence properties simultaneously indicative of multiple locations. We observe four principal microenvironments for Prodan, including an inner “free” water pool, a bound water region, the AOT interface, and the surrounding hydrocarbon solvent phase. As the parameters of surfactant concentration and the molar ratio of water to surfactant are varied, we attribute the observed emission characteristics of Prodan to specific micellar structural features including heterogeneity of the water pool, the variable polarities of the bound and free water regions, the hydrophobicity and permeability of the surfactant interface, and the hydration of Na+ counterions in the bound water region.