NOVELTY - The process of preparing topologies (4) on the surface of an organic thin layer (1) in liquid or gel form and based on a substrate (3), comprises performing localized projection of a liquid material immiscible with a material (5) constituting the thin layer. The material constituting thin layer is present as monomer solution, polymer solution, liquid monomers or polymer gel, or in the liquid form with a viscosity of 200-5000 cps. The thin layer has a thickness of greater greater than or equal to 20 mu m in its liquid or gel state. The material constituting the thin layer undergoes a gelatinization.    USE - The process is useful for preparing topologies on the surface of an organic thin layer in liquid or gel form and based on a substrate, which is useful in a fuel cell.    ADVANTAGE - The process is capable of easily and economically preparing topologies with different nature on the surface of an organic thin layer in liquid or gel form and based on a substrate, in a controlled manner, without affecting the characteristics and properties of the thin layer and the substrate.    DETAILED DESCRIPTION - The process of preparing topologies (4) on the surface of an organic thin layer (1) in liquid or gel form and based on a substrate (3), comprises performing localized projection of a liquid material immiscible with a material (5) constituting the thin layer. The material constituting thin layer is present as monomer solution, polymer solution, liquid monomers or polymer gel, or in the liquid form with a viscosity of 200-5000 cps. The thin layer has a thickness of greater greater than or equal to 20 mu m in its liquid or gel state. The material constituting the thin layer undergoes a gelatinization by photopolymerization or thermopolymerization before the projection step and evaporation and polymerization after the projection step. The immiscible liquid material is less dense than the material constituting the thin layer. The localized projection is made using a microdispensing head such as an inkjet-print head. The material constituting thin layer and/or non-miscible liquid material are subjected to evaporation and polymerization, after the projection step.    DESCRIPTION OF DRAWING(S) - The figure shows a sectional view of a fuel cell.    Organic thin layer (1)    Substrate (3)    Topologies (4)    Material constituting the thin layer (5)    Catalytic layer. (6)