Microemulsions are systems with unique characteristics that set them apart from conventional emulsions. With particle sizes that are 10 to 100 times smaller than those of standard emulsions, microemulsions are liquid, transparent, and thermodynamically stable systems that possess superb solubilizing and dispersing ability for difficult actives.

By definition, microemulsions consist of four components: aqueous phase, oily phase, a surfactant and a co-surfactant.
Unlike emulsions, they form micro droplets and/or swollen micelles with minimal mechanical energy input. A simple stirring of the right ingredients is sufficient to form a stable formulation, to which the active may be added with great ease.

Moreover, the fluidity of these systems permits sterilization of the formulation by ultra-filtration prior to packaging. Absence of heat combined with the low mechanical energy of the process may prove particularly useful with heat-sensitive actives.