Aberration corrected TEM/STEM was applied for the observations of functional materials for environmental and energy devices. Some experimental results are presented in this brief report. High resolution transmission electron microscopy (HRTEM) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) observations were carried out for Au on metal oxide catalysts in order to observe fine structure of Au particle and the interface between Au and metal oxide. Elemental mapping by energy dispersive X-ray spectroscopy (EDS) was also examined for Au/TiO₂ catalyst, and the distribution of Au particles was obtained in nano-scale. Electrode materials for Lithium ion batteries were also observed by STEM and electron energy loss spectroscopy (EELS). STEM-EELS spectrum imaging was performed for the Li_1.2Mn_0.4Fe_0.4O₂ positive electrode with high energy resolution using monochrometer. It enables us to estimate oxidation state of transition metals by energy loss near edge structure (ELNES).