The size of conventional optical devices — such as dielectric waveguides and optical fibres — is restricted by the diffraction limit for light. One way of achieving smaller photonic structures is to construct metal nanoparticle plasmon ‘waveguides’, as shown by Stefan Maier and colleagues in this issue. Metal nanoparticles can sustain collective oscillations of their conduction electrons, which, coupled with an external light field, form surface plasmon polaritons — a form of electromagnetic energy. For the first time, Maier and colleagues observe the transport of these plasmon polaritons a short distance along the surface of a metal nanoparticle chain (see cover image). (Text taken from the Nature Materials Webpage)