Placing a magnetic material such as iron or steel, in a strong magnetic field can make magnets. The atoms forming materials that can be easily magnetized such as iron, steel, nickel, and cobalt are arranged in small units, called domains. Each domain, although microscopic in size, contains millions of billions of atoms and each domain acts like a small magnet. If a magnetic material is placed in a strong magnetic field, the individual domains, which normally point in all directions, gradually swing around into the direction of the field. Placing a metal core (usually an iron alloy) inside a coil of wire carrying an electric current produces electromagnets. The electricity in the coil produces a magnetic field. Its strength depends on the strength of the electric current and the number of coils of wire. While the current flows, the core behaves like a magnet, but as soon as the current stops, the magnetic properties are lost. Electric motors, televisions, magnet trains, telephones, computers and many other modern devices use electromagnets. This type of rock was subsequently named magnetite, after either Magnesia or Magnes himself. Unlike amber (fossilized tree resin), magnetite was able to attract objects without first being rubbed. This made magnetite far more magical. People soon realized that magnetite not only attracted objects made of iron, but when made into the shape of a needle and floated on water, magnetite always pointed in a north-south direction creating a primitive compass. This led to an alternative name for magnetite, that of lodestone or "leading stone".