This essay shows how Fourier Transform infrared spectroscopy (FTIR) can be applied to study membrane phase behavior of cells that are relevant for biomedical applications such as red blood cells and platelets. FTIR studies are minimally invasive and do not require labeling. FTIR can give unique information on conformation and stability of membranes in cells that are exposed to heating, freezing or dehydration stress. By combining in situ FTIR techniques with cell viability studies, cell damage can be correlated with membrane phase changes. Understanding the complex behavior of biomembranes during heating, freezing and drying is directly relevant for thermal processing of cells such as is done in cryopreservation and cryosurgery.