We present a simulation model in order to study the formation of nanoparticles in microemulsions. It is observed that nucleation and growth appear on different time scales at high concentrations but overlaps at low concentrations. It is also observed that concentration can induce a separation of the two kinds of growth: autocatalysis and ripening. It has been found that the ripening mechanism is more significant as reactant excess and film flexibility increases because, when one of the reactants is exhausted, ripening is the only possible way of growth.