Some transition metal ions are widely distributed in biological systems in the form of metal-binding proteins and enzymes. They are involved in many important physiological actions such as metabolism of substances and energy, homeostasis of the cell, and so on. Biometal Science Laboratory have been studying to understand the action of the metal ions in metal-binding proteins/enzymes in molecular level on the basis of their molecular structures, which are determined by X-ray crystallography and several spectroscopies, in combination with biochemical, molecular biological and chemical techniques. Recently, we especially focus on membrane-integrated nitric oxide reductases, and proteis involved in cellular dynaimics of iron. In addition, we also design and construct a new instrument which allows a simultanous measurement of X-ray diffraction/scattering and IR spectrum on the SPring-8/SACLA beam line.