Emulsions are liquid preparations that typically contain a mixture of oil and water. The oil and water mix and are kept homogenized by the addition of an emulsifying agent of excipient. Excipients ensure that the oil phase is is kept finely dispersed throughout the water as minute globules. Emulsions are considered a type of liquid–liquid colloid. Emulsions are thermodynamically unstable as the dispersed and continuous phases can revert back as separate phases, oil and water, by fusion or coalescence of droplets. However, emulsions are commonly stabilized by an emulsifying agent, often referred to as a surfactant.