Fatty acids (FAs) are carboxylic acids with a long aliphatic chain, either saturated or unsaturated. FA vesicles are colloidal suspensions of closed lipid bilayers, which are composed of fatty acids and their ionized species (soap). They are observed in a small region within the fatty acid-soap-water ternary phase diagram above the chain melting temperature (Tm) of the corresponding fatty acid-soap mixture.