Water-in-oil microemulsions have been made with lecithin in the presence of some alcohols. The structure of the microemulsions has been studied by steady-state and time-resolved analysis of the luminescence quenching of Ru(bipy)(3)(2+) by Fe(CN)(6)(3-). We found that well-defined microemulsions can be made only in the presence of short-chain alcohols such as propanol-1 and butanol-1. There exists a threshold for water content in order to obtain typical reverse micelles. Thus in the case of propanol-1, water/surfactant ratio w(o) should be above 20. By varying water content in the range 20 < w(o) less than or equal to 40, the microemulsion droplets suffer dramatic structural changes and the system passes through a percolation threshold.