A plasmon is a quantum of plasma oscillation. The plasmon is a quasiparticle resulting from the quantisation of plasma oscillations just as photons and phonons are quantisations of light and heat. Plasmons are collective oscillations of the free electron gas density, for example, at optical frequencies. Plasmons can couple with a photon to create another quasiparticle called a plasma polariton. This book presents topical research data in the study of plasmons, including the profile control of the obtainable gold nanostructures for localised surface plasmon resonance application; cutting edge techniques to improve signal sensitivity and assay performance for surface plasmon resonance immunobiosensors; the application of surface plasmon resonance (SPR) technology for elucidating enzymatic reactions involving nucleic acids; and graded plasmonic structures and their properties.