The invention provides a new apparatus (20) and method for producing entirely new types of nanoparticles exhibiting novel properties. The apparatus comprises a vacuum chamber (22) containing a gas and feed means (1) for feeding a liquid jet (26) into the chamber and through the gas. The invention extends to the new types of nanoparticles per se, and to uses of such nanoparticles in various biomedical applications, such as in therapy and diagnosis, as well as in opto-electronics.