Emulsion a blend of two liquids where one forms tiny droplets which are evenly dispersed in the other. It is not strictly a mixture, because the two liquids do not actually mix. The technical term for combinations of this kind is a colloid. The blend may be stable, although in practice—and especially in cookery—emulsions often separate.
Common emulsions used in cookery are milk, cream, and butter, and made sauces such as mayonnaise. Butter is not usually thought of as a liquid, but it is a genuine emulsion. To understand why, it is necessary to examine the structure of these substances in some detail.