Nanomaterials used in sensors use a range of properties to detect environmental changes. These can include physical changes such as phase transitions or changes in electronic band gap structures that can affect optical and electronic properties. Selectivity can also be introduced by the addition of chemical "sockets" selective for particular analytes. This paper will outline some of the technologies available and will give specific examples of the development of hydrogen sensors produced by nano cluster deposition and chemical sensors produced using polymer nanotubes.