text: Localized surface plasmons are distinct from propagating surface plasmons. In localized surface plasmons, the electron cloud oscillates collectively. In propagating surface plasmons, the surface plasmon propagates back and forth between the ends of the structure. Propagating surface plasmons also need to have at least one dimension that is close to or longer than the wavelength of incident light. The waves created in propagating surface plasmons can also be tuned by controlling the geometry of the metal nanostructure.