Plasmonics studies the physical phenomena that occur when light interacts with metal or highly doped semiconductor structures. Oscillations of free charge carriers in such structures (plasmons) can interact with an external electromagnetic field. This leads to the appearance of plasmonpolaritons — waves, whose energy is made up of the plasmon energy and the photon energy. Unlike conventional electromagnetic waves, plasmon-polaritons possess a strong spatial localization at optical frequencies, which potentially allows the creation of optoelectronic devices, sensors and subwavelength lasers. In the framework of the course, the fundamental principles of the light interaction with material’s plasma oscillations will be considered, and methods for describing the plasmon properties of single metal nanoparticles and their arrays will be discussed.