The phenomenon of magnetic attraction by the lodestone has been known for thousands of years. The compass was the first practical application of magnetism, used in navigation in China in the tenth century AD. Another effect known for centuries was the attraction and repulsion between charged objects. In the nineteenth century, researchers started investigating the connection between these two phenomena. The decisive experiment was performed by Hans Oersted (1777–1851), who found that the needle of a compass moved when an electric current flowed in a nearby wire. Michael Faraday (1791–1867), in the same century, revealed the symmetric effect, i.e., magnets inducing an electric current. Many applications resulted from these discoveries, with the creation of new techniques and equipment. Medicine benefited, e.g., with the use of nuclear magnetic resonance or the magnetic properties of hemoglobin for images and the therapeutic and diagnostic use of magnetic nanoparticles. Only in the twentieth century, with the birth of quantum mechanics, was the physics of magnetism understood. How could one predict that this strange phenomenon would be used to preserve the memories of humankind? Today, information created at an accelerating rate is stored in magnetic tapes and magnetic hard disks.