Emulsions: Oily substances (this includes natural and synthetic oils, fats, waxes etc.) and water do not readily mix. However, with high energy mixing it is possible to disperse one liquid within another liquid. In an oil-in-water emulsion, oil is dispersed in tiny droplets throughout the external water phase. In a water-in-oil emulsion, tiny droplets of water are dispersed throughout the external oil phase. If emulsions are left undisturbed they will eventually return to their separate water and oil phases. By adding specific chemical substances (generally called emulsifiers) the phases not only mix together with more ease but the resulting emulsions can be stabilised for long periods of time. Stable emulsions are extensively used in the manufacture of many cosmetic products i.e. creams and lotions.