In Figure , the crystallisation of a supersaturated MgSO 4 solution over time is shown while the sample was being kept at approximately 4 °C. As expected, the spectrum of the MgSO 4 solution was completely featureless with a monotonously increasing baseline. Such spectral features are expected for aqueous solutions where no molecular order on the timescales of picoseconds is maintained and thus the molecules in solution are completely disordered in an amorphous phase. Over time the baseline dropped, and a peak emerged at 1.6 THz which showed the existence of crystals.