During the freezing process and in the frozen state, the drug substance encounters a variety of stresses. Freeze concentration, resulting from ice crystallization, can cause a significant increase in both viscosity and local ionic strength. Investigating the physicochemical properties of pharmaceutical formulations upon freezing is technically challenging due to their multiphase and multicomponent nature. In recent years, ssNMR and Synchrotron X-ray diffraction (SXRD) have been utilized as advanced techniques for this purpose, as summarized in Figure . This includes the development of ssNMR as an in-situ method to analyze microenvironmental properties across the entire freezing temperature range, from room temperature to ultracold temperatures (Figure ). For example, the freezing point and residual water content of Dupilumab formulations have been readily quantified (Figure ). This capability enables a comprehensive investigation of physicochemical attributes in freeze concentrates as elaborated below.