Multisegment Au/Ni/Au nanowires have been used as a model system to explore the dynamics of receptor-mediated self-assembly. Light microscopy (top) and fluorescence (bottom) images of a 300 nm diameter and 4.5 mu m long Au/Ni/Au nanowire are shown in the Figure, where the gold end segments have been functionalized with fluorescently labeled avidin to direct end-to-end assembly.