From a semi-classical point of view, the magnetization vector from an ensemble of identical nuclear spins K precesses around the direction of the magnetic field present at the position of the nuclei at a well-defined frequency, called Larmor frequency. This Larmor frequency is proportional to the magnetic field B loc experienced locally by the nucleus. B loc is determined by the external magnetic field (B 0 ), modified due to the local electronic structure around the nucleus, imparting nuclei in different local environments different Larmor frequencies. These small local differences in B loc and, hence, the Larmor frequencies are observed in NMR spectroscopy as nuclear shielding, a fundamental NMR property used to distinguish different nuclei in molecules.