One of the most important contributions of the research group to the general scientific knowledge is the observation and the explanation how various planar faults (twins, antiphase boundaries, inversion boundaries, polytypic sequences) in polycrystalline ceramic influence the phenomena of exaggerated and/or anisotropic grain growth. Namely, up to now known and accepted mechanisms for exaggerated and/or anisotropic grain growth did not acknowledge the predominant role that existing planar faults have on the microstructure evolution. With the explanation of nucleation mechanisms and determination of the structure and the chemical composition of various planar faults in technological important materials (varistors, dielectrics, etc.) by electron microscopy analytical techniques, we determined the thermodynamic and processing boundary conditions within which it is possible to control the microstructure evolution with the aid of planar faults. The knowledge of these boundary conditions enables us to prepare the materials with desired final physical properties since we can control the microstructure evolution by dopants and resulting planar faults. These findings are extremely important for materials science in general since they include new knowledge in microstructure evolution. The application values of these results were already successfully applied in development of ZnO-based varistors with planar faults-controled microstructure. The research group has also largely contributed to the development and implementation of electron microscopy analytical methods. In collaboration with numerous partners from abroad or by themselves, the research group has developed, improved or implemented the following analytical methods: the method for determination of polar axis in non- centrosymmetric crystals, the method for determining the chemical composition of sub-atomic layers, the method for quantitative interpretation of HAADF-STEM images, the so called WARP-method for processing of HAADF-STEM images, the method for evaluating EEL spectra and optimization of experimental parameters for quantitative WDS analysis of trace elements.