We developed a setup that can be used to observe crystallisation processes from aqueous and other organic solvents utilising terahertz time-domain spectroscopy in transmission geometry. Both static systems and systems under flow were investigated while either keeping the temperature constant or employing temperature ramping. Utilising the versatility of the setup, the system was studied at different temperatures before, during, and after crystals formed, thereby allowing the investigation of both crystals and the solvent at different levels of saturation.