Direct ink-jet printing of water-insoluble organic materials may provide a new route for low-cost fabrication of various products that require fine patterning of functional molecules. However, printing by water-based, environmentally friendly inks requires significant research and development efforts aimed at achieving a dispersion of nanoparticles of the specific molecule in water. We demonstrate a concept for direct patterning of water-insoluble organic molecules in the form of nanoparticles, which can be easily adapted to a large variety of molecules such as conducting polymers and organic light-emitting diodes. The method is based on formation of a thermodynamically stable oil-in-water microemulsion in which volatile "oil" droplets contain the dissolved organic molecules. The microemulsion droplets are converted into organic nanoparticles upon impact with the substrate surface due to evaporation of the volatile solvent.