O/W emulsions include the dispersed phase (oil) and the continuous phase (water). The dispersions are usually un- stable, so phase separation may occur as soon as stirring ceases. To make a kinetically stable emulsion, a third com-
ponent, surfactant, or emulsifier is required. Based on the droplet size of oil, O/W emulsion can be divided into three kinds: conventional emulsions in the micrometer range, miniemulsions with submicrometer droplet size, and mi- croemulsions with very small droplet sizes (typically 10 nm) [11].