It is demonstrated how microemulsions can be used as model systems to study a range of fundamental liquid state phenomena. By carefully characterizing a single ternary system it is possible to obtain both a qualitative understanding and a quantitative description using the concept of the curvature energy of the surfactant film at the water–oil interface. We demonstrate the approach on the following problems: calculation of the oil–water interfacial free energy; nucleation; Ostwald ripening; solubilization kinetics; the Hofmeister effect; macroemulsion stability; vesicle fusion and fission. For all these phenomena it is demonstrated that one can by combining experimental studies on water–oil–nonionic surfactant systems with a careful theoretical analysis obtain an understanding that goes beyond what has been achieved using conventional systems.