We report on the effects of temperature (+30 to −100 °C) and water loading on the steady-state fluorescencefrom four fluorescent probe molecules when they are sequestered within the interior of sodium bis(2-ethyl-1-hexyl) sulfosuccinate (Aerosol OT, AOT) reverse micelles. Each probe locates itself to differentaverage microenvironments within the reverse micelle, and these individual microenvironments behavedifferently to changes in the molar ratio of water-to-AOT (R) and temperature. Changes in probe steady-state fluorescence emission spectra or fluorescence anisotropy indicate that “freezing” occurs within thewater pool at temperatures between −10 and −60 °C. The lowest freezing points are generally observedat the lowest R values.