Fast Field Cycling NMR relaxometry is a non-destructive low-field magnetic resonance technique which is performed in the range of a few kHz up to around 100 MHz, depending on the instrument. FFC NMR relaxometry is the only low-field NMR technique which measures the longitudinal spin relaxation rate, R1=1/T1, as a function of the magnetic field strength over a wide range of frequencies using only one instrument. The information obtained from T1 is connected to the molecular dynamics of a substance or complex material. The technique is particularly useful in revealing information on slow molecular dynamics which can only be carried out at very low magnetic field strengths.