The magnetic properties of the sample can change between different regions of the sample, i.e. between air cavities and tissue. These changes of magnetic properties are responsible for local changes of the magnetic field strength, so called susceptibility field effects. Some imaging applications and most spectroscopy applications require very homogeneous magnetic fields across the region of interest. The susceptibility induced field changes between different regions of the sample can be (partially) compensated by the shim coils. This homogenization of the magnetic field is often called “shimming the sample”. For every new study, an automatic shimming process is started as a self-adjustment of the scanner.