The microsegmented flow principle was applied for the preparation of polymer minirods. A microfluidic assembly was used to form monomer segments separated by an immiscible perfluorinated aliphatic solvent. These segments were transformed into polymer rods by thermal polymerization. Uniform-sized polystyrene rods with various diameters and lengths were prepared in this way. The microfluidic geometry and polymerization conditions were tuned to obtain polymer rods of various lengths and diameters. Metal nanoparticle doped polystyrene polymer rods were obtained by thermal polymerization of appropriate nanoparticle/monomer mixtures. After polymerization, the polystyrene rods were colored by an azo coupling reaction.