Abstract: We highlight three aspects of NMR (nuclear magnetic resonance) and NSR (nuclear spin-rotation): (1) Relativistic theory of NMR: The nonrelativistic theory of NMR was established in 1950 by Ramsey, but the corresponding relativistic counterpart was long plagued by the `missing diamagnetism. This was fully resolved only in 2007. (2) Relativistic theory of NSR: The nonrelativistic theory of NSR was also established in 1950 by Ramsey. Because of the involvement of nuclear degrees of freedom, the proper formulation must invoke the body-fixed relativistic molecular Hamiltonians that are transformed rigorously from the space-fixed ones. Electrons are here treated fully relativistically, whereas nuclei are treated quasi-relativistically. (3) Relativistic mapping between NMR and NSR: The nonrelativistic relation between NMR shielding and NSR constant was again established in 1950 by Ramsey 1 and was later popularized by Flygare . According to this relation, a fully relativistic measurement (NSR constant) is translated into a nonrelativistic value, experimental NMR shielding. This is problematic even for F in HF: The relativistic effect is here ca. 5 ppm and larger by one order of magnitude than the error bar propagated from the uncertainty in the experimental measurement of NSR. It turns out that a direct relativistic mapping between NMR and NSR is possible, which allows to establish true experimental NMR shielding scales.