We are developing new spectroscopic techniques using 'soft X-rays' to investigate the electronic structure responsible for the electrical, magnetic, and optical properties of materials. In particular, we have focused on the potential of soft X-ray emission spectroscopy or resonant soft X-ray inelastic scattering to directly observe elementary excitations (crystal field excitations, spin excitations, magnon excitations, charge density wave excitations, orbiton excitations, etc.) in strongly correlated materials such as Mott insulators and new high-Tc superconductors. Our research interests include the electronic states of aqueous solutions and solid-liquid interfaces responsible for their functions, observation of microheterogeneities in water and their origin, electronic structure analysis of oxygen reduction catalysts for fuel cells, electrode materials for lithium-ion batteries, photocatalytic materials, and metalloproteins. We are conducting research on all kinds of materials to which soft X-ray emission spectroscopy can be applied. In addition, we are conducting R&D experiments to improve the efficiency and energy resolution of soft X-ray absorption and emission spectroscopy for high-brilliance synchrotron radiation sources. In addition, we are conducting many joint researches with companies for society related researches.