Many industrially crystallized compounds are obtained by nucleation and growth from solution. To fully understand crystallization processes, the parameters that influence the yield and stability of a desired crystalline form (solvents, concentrations, pH, stirrer geometry and speed, reactor geometry, temperature, pressure, etc.) are of particular interest. In this presentation, we show examples of the use of a slurry flow cell in research-scale experiments to prove the excellent suitability of the X-ray diffraction technique (XRD) for in situ crystallization studies.