"A key to understanding the processes operating in the outer part of the Earth is to look at the metamorphic rocks produced in orogenic belts. These rocks now exhumed to the Earth’s surface provide a record of what they experienced, if only they can be correctly interpreted.The recent use of high resolution devices has revealed the three-dimensional size, shape, composition and distribution of microstructural features in metamorphic rocks down to the nanometre-scale. The new observations show that mechanically maintained pressure variations can be significant (~1 GPa) even on a micro-scale. However, there is currently no satisfactory thermodynamic methodology for a quantitative interpretation of systems with such pressure variations in metamorphic rocks. Ignoring such pressure variations in petrological analysis can lead to errors in depth estimates that are comparable to the typical thickness of the whole continental crust. Such an error may then significantly influence the quality of geodynamic reconstructions.Here, I propose to develop a revolutionary theoretical and computational method to understand microstructures that reflect pressure variations, based on the chemical and mechanical properties of their constituent minerals. Using the novel theoretical approach, I and my team will perform 3D numerical simulations and give the criteria to correctly understand the key microstructures.This emerging multi-disciplinary research will provide a quantitative and physically-based framework for interpreting common microstructures in metamorphic rocks. Furthermore, the new approach will not only make a critical contribution to understanding the interplay between metamorphic processes and deformation on the grain scale, but it will also form the basis for a new generation of models for application to large-scale geological scenarios. The results of the project will thus significantly increase our understanding of key processes in the Earth’s lithosphere."