An imaging method uses a plurality of sets of carbon nanotubes. Within a set the carbon nanotubes carry markers for a respective receptor that is specific for the set and the carbon nanotubes have a geometry, characterized for example by a chiral number that gives rise to an electromagnetic absorption peak at a wavelength specific to the set. An image is formed by transmitting electromagnetic radiation to a body, substantially at the wavelengths of the absorption peaks of the sets, e.g. time multiplexed with each other, and detecting for example an ultrasound response to absorption of the transmitted electromagnetic radiation. Different images of the electromagnetic absorption as a function of position in the body are formed for different wavelengths.
