X-ray absorption fine structure (XAFS) is a powerful technique in characterization of structures and electronic states of materials in many research fields including catalysts, semiconductors, optical ingredients, magnetic materials, and surfaces. This characterization technique is possible not only in a static state but also in a dynamic state (in-situ condition). The XAFS can provide information that is not possible by other techniques for characterization of materials, particularly catalysts and related surfaces. Furthermore, XAFS can provide molecular-level approach to mechanistic study...