Highly concentrated oil-in-water-type emulsions are spontaneously formed by a rapid decrease in temperature in the 0.1 M NaCI aqueous solution/hexaethylene glycol dodecyl ether/monolaurin/n-decane system. The change in the self-organizing structures was monitored by electric conductivity and the results were interpreted on the basis of phase behavior, The spontaneous curvature of the surfactant molecular layer changes from concave to convex toward water with decreasing temperature, The reason is that surfactant self-organizing structures change from a water-in-oil microemulsion to a highly concentrated emulsion via lamellar liquid crystal and reverse bicontinuous (reverse L-3) phases. It is important to lower the temperature quickly to form stable highly concentrated emulsions with fine droplets, because the system passes through an extremely unstable emulsion region.