In alcohol–water binary mixtures, microheterogeneous clustering creates a non-ideal mixture. This molecular clustering in the binary mixture is controlled by relativity in the intermolecular interaction energies. This relativity-controlled clustering is inherent to the liquid state, irrespective of whether the solution is aqueous or non-aqueous. The vapor–liquid equilibrium for alcohol–water binary mixtures which represents non-ideality is correlated to relativity-controlled clustering. This paper was reviewed on the basis of our reported results, and presented at the 2012 EMLG/JMLG Annual Meeting in Eger.