The incorporation Of [Ru(bpy)(3)](2+) within microemulsions formed from anionic (AOT, sodium bis(2-ethylhexyl)sulfosuccinate) and cationic surfactants (CTAB, cetyltrimethylammoniurn bromide) has been investigated by steady-state and time-resolved emission spectroscopy as a function of water content (3 less than or equal to w(0) less than or equal to 15; w(0) = [H2O]/[surfactant]). For anionic surfactants, [Ru(bpy)(3)](2+) is localized at the surfactant interface, and its emission is characterized by monoexponential kinetics at all w(0) values. For cationic surfactants, the emission decay is strictly monoexponential at large w(0) values. At small w(0) values (< 10), the decay is biexponential, and time-resolved emission spectra reveal two discrete emission maxima. These results are interpreted as surfactant-probe interactions driving the formation of at least two different-sized nanodroplets.