Small particles that are not completely wetted by either oil or water have the tendency to absorb at the interface between the two phases. This can cause stabilisation of the interface: the particles partially stick out of the interface, giving steric hindrance for coalescence, just as non-ionic surfactants do. The colloidal particles form a very strong membrane around emulsion droplets. Emulsions stabilised with such particles are referred to as Pickering emulsions.