In most cases, the ideally mixed state of various kinds of molecules is the reference state. Deviations from that can be caused either by dissociation of the molecules, for instance into ions, and by association of molecules. As "like likes like", structures that develop are typically groups of one type of molecules embedded in an excess of the other molecules such as a dilute oil in water emulsion. The latter is a heterogeneous phase and arises because of associations between molecules. The pockets of molecules can go under various names, depending on the discipline/application: aggregates, flocs, associates, coagulates, etc.