Morphological data of material samples provide valuable insight into changes in the structure; changes in the size and form of crystallites, generation of voids as a consequence of cyclic stress experiments and changes in phase structure. Also additives in a formulation (fillers, pigments), processing history (flow direction in the mould filled up), welding line formation, flow fronts, mould temperature, impurities, etc., are important aspects that are studied by microscopy.