Plasmonics refers to the generation, detection, and manipulation of signals at optical frequencies along metal-dialectric interfaces at the nanometre scale. The four chapters of this book analyse plasmonics and its applications. Chapter One discusses the plasmonic sensor and its use in the detection of brain enzymes. Chapter Two examines the optical constants of plasmonic nanostructures and demonstrates that optical absorption can be used to estimate dielectric constants of noble metal nanostructures. Chapter Three theoretically investigates the magnetoplasmonics of noble metal nanostructures and shows that plasmonic nanostructures have increased magnetic response in visible range at low magnetic fields. Lastly, Chapter Four studies some aspects of classical and quantum optical effects in surface plasmonics.