Our knowledge of processes governing the evolution of the lithosphere heavily relies on modelling of phase equilibria in metamorphism. This session aims to bring together geochemists, geophysicists, petrologists, and experimentalists to discuss the advancement of methods for constraining the environmental conditions (pressure, temperature, redox conditions and/or chemical potential) and their evolution with time, the quantitative modelling of microstructures, and the applications on natural case histories to provide a robust framework for the understanding of metamorphism. We welcome contributions from experimental, field, and computational studies to promote an interdisciplinary approach to modelling natural complexity.