Being able to probe translational diffusion greatly increases the information content of magnetic resonance measurements. Such measurements in a freely diffusing system provide direct access to information on molecular size and intermolecular interactions. This is of fundamental importance in understanding reacting systems since diffusion is how the reactants come together and the reaction products disperse. Whereas in a translationally restricted system NMR diffusometry can probe the size and anisotropy of the restrictions. Further NMR diffusion measurements can be combined with imaging to study spatially heterogeneous samples and with relaxation measurements to gain further information on the molecular dynamics. Together NMR diffusion measurements lead to an extraordinary range of applications including clinical diagnostics, pharmaceutical screening and probing associating systems. Traditionally magnetic gradient-based NMR spin-echo diffusion measurements have been performed on systems which are time stationary which facilitates separation of relaxation-based attenuation from diffusion-based attenuation. However, in reacting systems the populations of the diffusing species are not time intransient and even the relaxivity can be time-dependent which can greatly complicate the separation of diffusive attenuation from relaxation-based attenuation and the subsequent analysis. By performing the measurements more rapidly it may be possible to transform a changing system into a pseudo-stationary system. But when the timescale of the changes decrease further and approach the timescale of the NMR diffusion measurement additional modifications to the measurements and the analysis are required to correctly interpret the data.