In chemistry, a micelle (also micella, plural micellae) is a particular grouping of molecules. Surfactants form micelles when they reach the critical micelle concentration (CMC). Surfactants are a chemical amphipathic compounds. It means that they contain both hydrophobic and hydrophilic ends and will therefor be attracted to the surface of the polar phase. Surfactants first will line up along the surface of the polar phase, and when that is completely filled up, they will begin to form micelles of different shapes, dependent on their concentration. The micelles are a grouping of surfactant molecules where either the hydrophobic (in a polar continuous phase) or the hydrophillic (in a nonpolar continuous phase) ends cluster inward to escape the continuous phase. When surfactants are present above the CMC, they act as emulsifiers. For instance, in a polar continuous phase, nonpolar compounds, such as oils, will be absorbed into the micelle and emulsified into the polar phase. This is what happens when you wash your hands with soap. It is also the basis for emulsion polymerization.

See also: vesicle