The aim of the proposal is to improve understanding about combinations of normal surfactants and hydrotropes. The systems of study are reference oil-water interfaces, provided by w/o microemulsions stabilized by AOT. Different additives will be investigated following an evolution of molecular structures, starting with a true hydrotrope, moving to an alkyl hydrotrope, and ending with a chemically related true surfactant. Such alkyl hydrotropes have chemical properties part way between the two extremes, comprising both surfactant (alkyl tail) and hydrotrope (head group) features. Although they are interesting colloidal stabilizers in their own right, there is only limited scientific literature to consult. Such hydrotropic additives are of great industrial interest, exhibiting detergency efficiencies in both aqueous and oil phases.