By use of X-ray and neutron scattering, densitometry and calorimetry as well as fluorescence, NMR and FT-IR spectroscopy, the temperature and pressure dependent structure, dynamics and phase behavior of a variety of lipid and model biomembrane systems was studied. Hydrostatic pressure was used as a physical parameter for studying the stability and energetics of lyotropic lipid mesophases, but also because high pressure is an important feature of certain natural membrane environments. Neutron scattering in combination with the H/D contrast variation technique and fluorescence microscopy was used to the study of lateral organization of phase-separated lipid mixtures. We also present data on the effect of incorporating polypeptides on the structure and phase behavior of lipid bilayers. By using the pressure-jump relaxation technique in combination with time-resolved synchrotron X-ray diffraction, the kinetics and mechanisms of different lipid phase transformations was also investigated. The technique has also been applied for studying other soft-matter and biomolecular phase transformations, such as protein unfolding. We present data on the pressure-induced unfolding and refolding of small proteins. The data are compared with the corresponding results obtained using other trigger mechanisms and are discussed in the light of recent theoretical approaches of protein folding.