This book focuses on recent interconnected topics in nanophotonics written by scientists at the forefront of these fields. The book presents results of numerical investigations of light-matter interactions at the nanoscale and in the attosecond regime using first-principles calculations while also discussing recent experimental developments of higher-order harmonic generation for the field of attosecond science. In addition to this, the book reviews recent advances in select topical areas such as highly efficiency solid-state light sources based on nanophotonics, plasmonic photochemical water splitting for efficient energy harvesting, and optical spectroscopy of single-walled carbon nanotubes with quite rich physics for future application in photonics.