In this work the inverse (water-in-oil) microemulsion polymerization of N-isopropylacrylamide (NIPA) at 25 °C is reported to produce PNIPA nanoparticles dispersed in PNIPA matrix in one step. Initially the reaction was carried out in batch mode and in order to increase the ratio polymer/surfactant, the reaction was continued by subsequent addition of monomer. The novelty of this work is that instead of latex containing dispersed nanogels, we obtained nanostructured macrogeles, which absorb more water than a conventional poly (N-isopropylacrylamide) hydrogel synthesized in solution with the advantage that Young´s module is greater than that of traditional hydrogels although the volume transition temperature does not change.