The Wheeler-Widom lattice mixture of three bifunctional molecules AA, BB and ab with finite interactions is analysed. It is shown that the model's properties are exactly obtainable in terms of those of the spin-1 Ising magnet. When the character of AA as "water" BB as "oil" and ab as "surfactant" is gradually emphasized, the microemulsion and liquid-crystalline properties develop from those of conventional mixtures. Amongst the former we have the Kahlweit scheme for three-phase coexistence, Winsor-type phase progressions and surfactant-film–supported microstructures.