This document defines and compares different types of emulsions including multiple emulsions, microemulsions, nanoemulsions, and nanosuspensions. It explains that emulsions are mixtures of two immiscible liquids stabilized by an emulsifying agent, while microemulsions are more thermodynamically stable with smaller droplet sizes. Nanoemulsions have droplets between 5-200nm and are kinetically stable. Nanosuspensions are solid drug particles less than 1um suspended in water stabilized by surfactants to improve dissolution and bioavailability. The document provides details on identification tests, preparation methods, advantages and disadvantages of these various emulsion systems.