Bicontinuous jammed emulsions (or bijels) are tortuous, interconnected structures of two immiscible liquids, kinetically trapped by colloidal particles that are irreversibly bound to the oil-water interface(1,2). A wealth of applications has been proposed for bijels in catalysis, energy storage and molecular encapsulation(3-5), but large domain sizes (on the order of 5 mu m or larger) and difficulty in fabrication pose major barriers to their use(6-8). Here, we show that bijels with sub-micrometre domains can be formed via homogenization, rather than spinodal decomposition. We achieve this by using nanoparticle surfactants: polymers and nanoparticles of complementary functionality (for example, ion-pairing) that bind to one another at the oil-water interface(9,10). This allows the stabilization of the bijel far from the demixing point of the liquids, with interfacial tensions on the order of 20 mN m(-1). Furthermore, our strategy is extremely versatile, as solvent, nanoparticle and ligand can all be varied.