Solid-state NMR spectroscopy represents a powerful tool to access information on chemical structure, dynamics and reactivity at molecular level on solid compounds and materials. Transition metal complexes represent an unrestricted source of examples for solid-state dynamics and reactivity due to the presence of highly mobile groups, very reactive ligands and the possibility of expanding the coordination sphere. The key question of the influence of the mobility on the reactivity of a system is the occasion for presenting several selected examples of solid-state dynamics and reactivity of transition metal complexes. Although only few unambiguous examples are reported in which this correlation has been investigated, this review presents the central role of solid-state NMR spectroscopy in the investigation of ligand motion, transformation mechanisms, kinetics and products of solid-state reactions in transition metal complexes. The aim of this microreview is to offer the state-of-the-art on this subject in order to develop new insights and to promote cooperative efforts in this fascinating field. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)