This seminar reviews ongoing experimental and theoretical efforts to explore the plasmonic response in metallic nanoparticles, where nanometric dimensions are expected to promote a nonlocal plasmonic response beyond that of the usual classical electrodynamics. I will review efforts in semi-classical hydrodynamic extensions to classical electrodynamics [1,2], as well as our most recent developments beyond these simplified models [3,4]. I will also address recent single-particle electron energy-loss spectroscopy (EELS) observations of higher-order modes in silver nanoparticles . Beyond the more fundamental aspects I will also discuss applications of nanoplasmonic systems, where localized plasmon resonances are used to facilitate a broad range of plasmonic colours with applications in decoration of plastic surfaces  and with novel opportunities for laser-post processing and printing of colours with subwavelength resolution .
 N.A. Mortensen, S. Raza, M. Wubs, T. Søndergaard, and S.I. Bozhevolnyi, "A generalized non-local optical response theory for plasmonic nanostructures", Nature Communications 5, 3809 (2014)
 S. Raza, S.I. Bozhevolnyi, M. Wubs, and N.A. Mortensen, "Nonlocal optical response in metallic nanostructures", J. Phys. Cond. Matter. 27, 183204 (2015)
 G. Toscano, J. Straubel, A. Kwiatkowski, C. Rockstuhl, F. Evers, H. Xu, N. A. Mortensen, and M. Wubs, "Resonance shifts and spill-out effects in self-consistent hydrodynamic nanoplasmonics," Nature Communications 6, 7132, (2015)
 W. Yan, M. Wubs, and N. A. Mortensen, "Projected-dipole model for quantum plasmonics," "Projected Dipole Model for Quantum Plasmonics", Phys. Rev. Lett. 115, 137403 (2015)
 S. Raza, S. Kadkhodazadeh, T. Christensen, M. Di Vece, M. Wubs, N.A. Mortensen, and N. Stenger, "Multipole plasmons and their disappearance in few-nanometer silver nanoparticles", Nature Communications 6, 8788 (2015)
 J. Clausen, E. Hojlund-Nielsen, A. Christiansen, S. Yaszdi, M. Grajower, H. Taha, U. Levy, A. Kristensen, and N.A. Mortensen, "Plasmonic metasurfaces for coloration of plastic consumer products", Nano Lett. 14, 4499 (2014)
 X. Zhu, C. Vannahme, E. Hojlund-Nielsen, N.A. Mortensen, and A. Kristensen, "Plasmonic colour laser printing", Nature Nanotechnology 11, 325 (2016)
N. Asger Mortensen is a full professor at the Technical University of Denmark (faculty since 2004), from where he also received the MSc (1998), PhD (2001), and Dr. Techn. (2006) degrees. His research focuses on wave phenomena and light-matter interactions in artificially structured materials. The list of past and present research topics include quantum electron transport in mesoscopic systems, photonic bandgap materials, nanofluidics & optofluidics, nanophotonics & slow-light photonic crystals, metamaterials, and nanoplasmonics. Among several honors, he is a fellow of SPIE. For more details, please visit www.mortensen-lab.org.