A micelle consists of a hydrophobic (water-repelling) core and a hydrophilic (water-loving) shell. Micelles may be spherical or cylindrical in shape. They may range in size from 2 nm to 20 nm, depending on the composition and concentration of micelles. The core is made up of the hydrophobic, nonpolar ends of amphiphilic molecules, typically hydrocarbons or lipids. The shell is composed of the hydrophilic, polar head groups such as carboxylates or phosphates. Their shape and structure make micelles particularly valuable for solubilizing hydrophobic compounds in aqueous conditions.