An interfacial Maillard reaction between furfural and cysteine in two different food-grade nano-sized self-assembled solutions with two oppositely curved interfaces (W/O and O/W microemulsions) have been studied and compared. These microemulsions are selective microreactors strongly enhancing the generation of sulfur-containing flavors. The Maillard reactions occur at lower temperatures than in water and are much faster. The interfaces of both W/O and O/W microemulsions are capable of enhancing the Maillard reactions in which the selectivity and reactivity are controlled by the composition of the interface and its curvature. In the W/O microemulsions the Maillard reaction was controlled and enhanced by the interfacial concentration of a co-emulsifier such as butanol and are restricted by the concentration of the core water reservoir. On the other hand,, in the O/W microemulsions, where water is the continuous phase, the reaction rates are enhanced by increase in the water content and the microemulsion curvature. The Maillard product internal composition (regioselectivity and type of products) is dictated by temperature, time, pH and mainly by the nature of the interface, and by the surfactant nature and its interfacial composition.