The invention concerns a process for the continuous treatment of an emulsion and/or a micro-emulsion assisted by an “expanded liquid” for the production of micro- and/or nano-particles or micro- and/or nano-spheres containing one or more active ingredients. In particular, a liquid solvent expanded by compressed or supercritical CO2 is contacted with an O/W emulsion, or alternatively a W/O emulsion or multiple emulsions, formed by an external phase that is itself a liquid expanded by compressed CO2. The expanded liquid forms a solution with the dispersed phase of the emulsion and extracts it inducing the formation of the desired particles of the dissolved compounds.The process is carried out in a counter-current packed column wherein the expanded emulsion is fed from the top, while the expanded liquid is fed from the bottom. Thanks to the presence of the expanded liquid, any deposition of the solid particles produced on the packing elements is avoided, thus preventing any column blockage. A suspension of micro-structured particles of the desired product can be collected continuously at the bottom of the column.