(Figure Presented) Bionanoparticles, such as the cowpea mosaic virus, can stabilize oil droplets in aqueous solutions by self-assembly at liquid interfaces. Subsequent cross-linking of the bionanoparticles transforms the assemblies into robust membranes that have covalent inter-bionanoparticle connections. The resulting membranes are nanoscopically thin sheets (see SANS image (SANS = small-angle neutron scattering)), which were examined by fluorescent labeling.