Functionalised nanoparticles have been used in a number of studies including detection of DNA at ultra low concentrations, immuno-histochemistry and more recently as substrates for surface enhanced resonance Raman scattering (SERRS) based imaging approaches. The advantages of using metallic nanoparticles are that they are very bright in terms of their optical characteristics and also can be functionalised to provide a SERRS response and hence provide a unique Raman fingerprint. Here we present the functionalisation of gold and silver nanoparticles in such a way that the enhancement effect can be greatly increased through biological interaction and as such effectively turn on the SERRS effect. In an advancement of this nanoparticles have been used as imaging agents for single cells when functionalised with an appropriate antibody and can give information on the expression of specific receptors on cell surfaces as well as sub-cellular compartmentalisation information.