Aizpurua studies the excitation of localized surface plasmons in metallic particles induced by a variety of external probes, including light. Among others he has developed theory to understand the excitation of surface plasmons in Scanning Transmission Electron Microscopy (STEM), in Scanning Tunneling Microscopy (STM), in Surface-Enhanced Raman Scattering (SERS), in Surface-Enhanced Infrared Absorption (SEIRA), or in Scattering-type Near-field Optical Microscopy (s-SNOM), among others. The understanding of the optical response of metallic nanoantennas in all these situations has been the main focus of his research during the last years.