The incorporation of functional nanoparticles within block copolymer micelles can form hybrid materials with desired optical, electronic, and magnetic properties. A versatile approach was developed to prepare ultralong nanofibers through the cooperative assembly of block copolymers and nanoparticles in emulsions. Enthalpic and entropic factors collectively contributed to the synergistic assembly of block copolymers and nanoparticles for the formation of uniform hybrids. The nanoparticles were precisely aligned in the central cores of the nanofibers which can reach to tens of micrometers. The u...