Increasingly functional colloidal particles (nanoparticles) are finding new applications in a wide range of both established and emerging technologies. This article describes the synthesis of such particles, from classical and naturally occurring colloidal particles to more recent, highly designed particles having some particular structure and physical properties, usually with a specific application in mind. The systems described range from inorganic particles (ionic salts and metal particles, through to modern graphene-based particles), polymer latex particles (including non-spherical, liquid and electrically conducting polymer particles), composite particles (in particular core/shell particles) and finally porous and swellable particles (microgels). Throughout, various applications are considered, in particular, one that I have been strongly involved with, namely controlled uptake and release from functional colloidal particles.