Magnet is not invented, it is a natural magnetite. Ancient Chinese people discover nature a kind of natural Magnetized stone, called "magnet." This stone can magically pick up small pieces of iron sheet, and after swinging freely always point in the same direction. Early sailors put this magnet as its earliest compass to identify the direction of the sea. The earliest discovery and use magnets should be Chinese people, or "Compass," is one of the four great inventions of China. After thousands of years of development, today has become a magnet strong material in our lives. By alloy synthesis of different materials to achieve the same effect with the magnet, but also can improve the magnetic force. In the 18th century there have been man-made magnets, but the manufacturing process is very stronger magnetic slowly until the 1920s to produce aluminum-nickel-cobalt (Alnico). Subsequently, the 1950s produced the ferrite (Ferrite), 70 years of manufacture rare earth magnets [Rare Earth magnet includes neodymium (NdFeB) and samarium cobalt (SmCo)]. Thus, magnetic science and technology has been rapid development of magnetic materials also makes the device more compact.