NOVELTY - Composition (A) for applying active agent (I) to a substrate comprises (A) dissolved in a micro-emulsion containing a foaming agent (II) and optionally a foam former (III) such that (A) foams on a substrate, (II) and (III) do not diffuse into the discontinuous phase particles and the microemulsion particles remain intact and are retained on the substrate when the foam subsides.    USE - (A) is specifically used for applying a pharmaceutical agent (especially dexpanthenol), a cosmetic agent or a biotechnological agent (especially a protein or peptide) to the skin; or for application of industrial active agents to substrates (all claimed). The industrial active agents are e.g. lubricants or markers (specifically pigments).    ADVANTAGE - After application to the substrate, the foam collapses to give a thin condensed film from which (A) diffuses continuously into the substrate over a long period. (I) can be applied accurately and reproducibly to target areas, in particular accurate doses of topical/dermal pharmaceutical or cosmetic active agents can be applied in high bioavailability form to the required site of action.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (a) a method for applying (I) to a substrate using (A);    (b) production of the microemulsion by forming a microemulsion preconcentrate, mixing the preconcentrate with water or an aqueous medium so that a microemulsion is spontaneously formed and adding (II) and optionally (III);    (c) a microemulsion for applying (I) to substrate, which contains (II) and optionally (III);    (d) a microemulsion preconcentrate comprising a mixture of a medium-chain triglyceride (IV) and an omega-9- and/or omega-6-fatty acid (V) together with a surface-active component containing a polyoxyethylene type surfactant;    (e) an alternative microemulsion concentrate comprising a phospholipid (VI), a natural or (semi-)synthetic di- or triglyceride and optionally a wax or fatty alcohol (or their derivatives or mixtures), together with a surface-active component as in (d);    (f) microemulsions obtained by mixing the preconcentrates (d) or (e) with water or an aqueous medium; and    (g) vessels containing the microemulsion (or a combination of the preconcentrate and an aqueous phase).