This comprehensive two-volume graduate textbook presents the theoretical basis of optics and spectroscopy together with their advancement to the nanoscale, relevant experimental and numerical techniques, and selected emerging applications of nanospectroscopy. The work aims at students of the natural sciences and interested readers entering this fascinating interdisciplinary field. Volume 2 covers theoretical and experimental methods essential for nanospectroscopy. The work explains necessary instrumentation, gives insights into simulation tools and introduces a wide variety of nanomaterials typically investigated by nanospectroscopy. Vol. 1: Fundamentals & Methods. The work "Optical Nanospectroscopy. Applications" presents numerous examples in modern photonics and optical sensing or state-of-the-art applications in material, chemical and biological sciences.