In this study, we confirmed the existence of a short-lived amorphous precursor phase involved in the formation of crystalline struvite. Coincident with the formation of solid particles, the supramolecular structure of the aqueous solution changed during nucleation and crystallization. We interpreted the evolution of the scattering intensity and extent of the Ornstein-Zernike density fluctuations as an indicator of liquid-liquid phase separation events participating in a nucleation pathway towards crystalline struvite. These concepts are summarised in Fig. . Our work demonstrates for the first time that a holistic analysis of time-resolved scattering patterns is a powerful tool to follow phase separation processes, be they a liquid-liquid demixing or nucleation and growth processes.