In HR relaxometry, cross relaxation during the transfer between high and low magnetic fields is often not negligible, which leads to deviations of the decay rate from the longitudinal relaxation rate, as observed in the first investigation by Kern and Redfield. Several approaches have been implemented to take these effects into account. Alternatively, a two-field NMR spectrometer, with radiofrequency pulses at the low-field center, allows to select the proper nuclear spin operator at low field and suppress cross-relaxation pathways during the relaxation delay. In addition, both transverse and longitudinal relaxation rates can be measured. The combination of high-field relaxation rates and relaxation rates at a single low provided more information than high-field relaxation alone when specifically labeled 1 methyl groups of isoleucine residues in ubiquitin were considered as shown in Figure .