Defect microstructures constitute a unique source of information about the formation and subsequent evolution of meteoritic minerals under various physical and chemical conditions. Such microstructures are, for example, dislocations, twins, domain structures, and exsolution lamellae. We aim at applying state-of-the-art electron-microscopic methods to explore the mineral microstructures of HAYABUSA samples returned from asteroid Itokawa in order to constrain the shock metamorphism, space weathering, and thermal evolution of an asteroid regolith. Questions of particular interest are: What and how are shock deformation features distributed among the regolith grains? What are the effects from residence on the air-less asteroid surface, particularly due to bombardment with microparticles and irradiation by cosmic rays? What is the degree of mixing of lithologies with different metamorphic histories due to the rubble pile nature of asteroid Itokawa? The central method for the proposed investigations will be analytical energy- filtered transmission electron microscopy (TEM), for which samples will be prepared by precise focused ion beam (FIB) milling. We plan to primarily focus on pyroxenes and olivines, because they are most abundant among HAYABUSA grains. Samples containing feldspar and pyrrhotite are however also requested since they are diagnostic shock indicators, also crystallographically and compositionally variable, with rich inventories of microstructures.