Micelle

A roughly spherical aggregate of amphipathic molecules, with hydrophobic regions gathered inside and hydrophilic regions exposed to the surrounding medium.

Amphiphile: A molecule with distinct hydrophilic and hydrophobic regions. Micelles assemble from amphiphiles whose contrasting regions orient toward water and away from it.
Hydrophilic: Having an affinity for water or other polar substances. Hydrophilic groups usually face outward toward the aqueous medium.
Emulsion: A mixture of droplets of one liquid dispersed in another liquid that does not normally mix with it. Unlike an emulsion, a micelle is an aggregate of amphiphiles rather than droplets of bulk liquid.
Bilayer: A sheet of two amphiphile layers with hydrophobic regions between hydrophilic surfaces. Bilayers form extended sheets rather than compact micelle interiors.
Critical micelle concentration: The concentration above which surfactant molecules spontaneously form micelles in a solution. It marks the threshold at which aggregation becomes favorable in a given solution.
Hydrophobic: Having little affinity for water and tending to avoid contact with it. Hydrophobic groups are gathered away from water in the micelle interior.
Detergent: A cleansing substance containing surfactants that help disperse oils and dirt in water. Detergent micelles can enclose oily material and carry it into the wash water.
Liposome: A spherical vesicle bounded by one or more lipid bilayers and enclosing an aqueous compartment. A liposome has a bilayer wall and watery core; a micelle has a hydrophobic core.
Hydrophobic effect: The tendency of nonpolar substances to aggregate in water as water molecules reorganize around them. It helps drive hydrophobic regions into the micelle’s interior.
Amphipathic molecule: A molecule with both water-attracting and water-avoiding regions. This molecular architecture allows micelles to form in polar solvents.

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