Microstructures play a fundamental role in deciphering the rheology of the lithosphere and lithospheric tectonics. Microstructures and crystallographic textures are used to analyze the physical and chemical properties of geomaterials, while deformation microstructures (e.g., fabrics, textures, grain sizes, shapes, cracks, etc.) can be used to infer, identify, and quantify deformation, metamorphic, magmatic or diagenetic processes. Processes such as grain-size reduction, metamorphic reactions, crack growth, and the development of crystallographic preferred orientations modify the rheological properties of rocks and minerals, providing key information on the dynamics of small- to large-scale tectonic processes. In this session, we invite contributions that use microstructure and texture analyses from field observations, laboratory experiments, and numerical modelling at brittle and/or ductile conditions aiming to constrain deformation mechanisms.