In spin crossover (SCO) complexes, two discrete electronic spin states (high spin (HS) and low spin (LS)) are available. The different number of unpaired electrons in the HS and LS states gives access to distinct magnetic and spectroscopic properties. As a result, futuristic applications of SCO complexes in spintronics and as sensing and memory devices have been suggested. Transitions between the HS and LS states can be induced by various external stimuli, including pressure. An example is the prototypcal [Fe(phen) 2 (NCS) 2 ] complex, in which pressure leads to a decrease in the metal-ligand distances and to an accompanying increase in the ligand field splitting energy, followed by SCO from the HS to the LS state (Figure ). Here, the focus lies on pressure-induced SCO in molecular metalligand complexes, but it must be noted that polymeric and non-molecular crystalline SCO systems are abundant, some of which have important implications for the magnetic properties of Earth's interior.