The prediction of synergistic effects between two self-organizing systems is tested. In situ grazing-incidence small-angle X-ray scattering (see figure) is used during thermal annealing of a nanoparticle-copolymer mixture, and shows that the orientation of the microdomains begins at the free surface and propagates in the film towards the substrate. This synergistic interaction is shown to apply to both cylindrical and lamellar block-copolymer morphologies.