Micelle
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In chemistry, a micelle (also micella, plural micellae) is an aggregate (or cluster) of surfactant molecules. Micelles only form when the concentration of surfactant is greater than the critical micelle concentration (CMC). Surfactants are chemicals that are amphipathic, which means that they contain both hydrophobic and hydrophilic groups. Micelles can exist in different shapes, including spherical, cylindrical, and discoidal.
In an aqueous or other polar solvent, the core of a micelle consists of the hydrophobic portion of the molecules, while the hydrophilic groups remain on the surface of the molecule so that they can maintain favorable contact with water. In a nonpolar solvent, the hydrophilic groups form the core of the micelle, and the hydrophobic groups remain on the surface of the micelle.
When surfactants are present above the CMC, they can act as emulsifiers. For instance, micelles formed by detergents in water assist in cleaning by incorporating hydrophobic material (such as oil, grease, or dirt) into their core. This is what happens when you wash your hands with soap. It is also the basis for emulsion polymerization.