Magnetic hyperthermia is the name given to an experimental cancer treatment, although it has also been investigated for the treatment of other ailments, such as bacterial infections. It is based on the fact that magnetic nanoparticles, when subjected to an alternating magnetic field, produce heat. As a consequence, if magnetic nanoparticles are put inside a tumor and the whole patient is placed in an alternating magnetic field of well-chosen amplitude and frequency, the tumor temperature would rise. This treatment method has entered phase II trials (in humans) only in Europe, but research is done in several laboratories around the world to test and develop this technique further.