Electrons and galaxies are physical objects whose sizes differ by a factor of 1036; both produce magnetic fields in their neighborhood. The Sun, other stars, and the terrestrial globe are also magnetically active, and this property is explained by the dynamo modeldynamo model, based on the rotation of a magnetic body. The fieldfield produced by the Sun extends for thousands of kilometers and can be felt on the Earth. Some neutron stars have a much higher field than the Sun, the highest found anywhere in the universe, in the range of 1012 T (or 1016 G); these are the magnetars. The Earth field is felt by the living beings on the planet, who, in some cases, make use of this field for orientation; these include bacteria, birds, and fishes. In the case of bacteria, it was found that they contain microscopic magnetic particles, whose magnetization is oriented by the Earth’s field. A phenomenon that has been used for many applications is that of nuclear magnetic resonancenuclear magnetic resonance (NMR), where an electromagnetic wave induces transitions in the system nucleus-magnetic field. Applications of NMR include nondestructive analysis of chemicals and applications in medicine, such as magnetic resonance imagingmagnetic resonance imaging (MRI) (MRI) and functional magnetic resonance imagingmagnetic resonance imaging (MRI) (fMRI).