This feature article focuses on the synthesis of noble metal nanoparticles and how these particles can be incorporated into thin films. The functional properties of the nanoparticles when embedded in a host matrix are covered. In particular the optical properties of noble metal nanoparticles, numerical theory, including Mie and Maxwell–Garnet equations are explained with particular attention on photoluminescence, photochromic and electrochromic properties. The dielectric effect of the host matrix and the influence on the surface plasmon resonance are explored. Future research applications and trends in the field are highlighted.