This book features a collection of reviews focusing on interrelated topics in nano-optics and nanophononics written by some of the world's leading scientists in these fields. The book discusses recent results of numerical investigations of light-matter interactions at the nanoscale using first-principles calculations. Additionally, it reviews selected topics in the areas of nanophotonic devices based on functional nanoparticles for energy harvesting and the development of photo materials for advanced applications in optics and nanotechnologies. Finally, the book reviews the experimental development of quantum-dot single-photon sources on integrated photonic circuits and looks at applications in quantum information processing and quantum information distribution based on color center in diamond.