A material in which one of the components has at least one dimension that is about 100 nanometres. This can include materials such as colloids and gels but is usually interpreted as being a combination of a larger phase called ‘the bulk’ with a phase at the nanometre scale having different physical and/or chemical properties. Nanocomposites have different properties from ordinary composite materials because in nanocomposite materials the ratio of the surface area to the volume of the phase with nanometre dimensions is high.