One of the main objectives of optics is the control of light propagation and confinement. Progress in optics historically started with the development of bulky lenses and mirrors, then prisms and gratings, and so on. The improvement of these devices slew down as the diffraction limit was approached. Nanophotonics aims at manipulating electromagnetic waves at sub-wavelength scale to go beyond this limit. The recent evolution of fabrication technologies, numerical tools and theoretical models opened the way to novel devices with unprecedented performances.