Electricity and magnetism are closely related: Power lines generate a magnetic field, rotating magnets in a generator produce electricity. However, the phenomenon is much more complicated: electrical and magnetic properties of certain materials are also coupled with each other. Electrical properties of some crystals can be influenced by magnetic fields—and vice versa. In this case one speaks of a "magnetoelectric effect." It plays an important technological role, for example in certain types of sensors or in the search for new concepts of data storage.