A higher magnification imaging (Fig. , middle) revealed that these aggregates are composed of near-spherical particles with diameters of ~40-50 nm. Selective area electron diffraction (SAED) from the aggregates (Fig. , right) indicated that the observed particles were amorphous. The inset in Fig. , highlights that these amorphous particles coalesce and are of low-electron density, which could be an indicator of an originally liquid-like character before cryo-quenching. After 60 s micron-sized single crystals of struvite readily developed in the solution (Fig. , left and middle), as was evident from the observed characteristic facetting, and the SAED exhibited only single diffraction spots assigned to struvite (Fig. , right). The morphology of the amorphous particles and their aggregates in Fig. is emulsion-like. Such structures have been observed for other systems with a prevalent amorphous phase and have been interpreted as a consequence of a liquid-liquid phase separation process preceding crystallisation . Noteworthy, the presence of these aggregates seems to be correlated with thicker vitrified ice in our cryo-TEM images, leading to an increased contrast ("false purple" patches in Fig. , left). We found thicker ice only in association with amorphous aggregates in all our experiments. We hypothesise that the observed correlation between the aggregates and the thicker ice may indicate a micron-size liquid-liquid phase separation. Such morphologies are absent when the crystals are already formed, and ice appears to be homogenous in thickness (Fig. ). Elemental