Magnets were one of the first natural forces to be discovered by humans. Their history dates back to the 4th century BC when Chinese literature referred to the attraction between iron and lodestone. Lodestone is a natural permanent magnet, meaning it creates its own magnetic field; this is what attracts the iron, which is an “induced” magnet i.e. it becomes temporarily magnetized when it comes into contact with a permanent magnet. A ferrofluid is an induced magnet in liquid form; the liquid becomes magnetized in the presence of a magnetic field.