The mission of Yamamoto Lab is to elucidate the working mechanisms of functional materials using the state-ofthe- art synchrotron radiation X-rays and establish design guidelines for developing novel functional materials. To realize this goal, we develop optical elements, optical techniques, and novel measurement methods to take full advantage of brilliant X-ray light sources such as NanoTerasu (Fig. 1). In particular, we focus on the development of “operando” measurement methods that enable direct observation of materials under operation, such as catalysts and batteries. We are also conducting research on the application of soft X-ray optical elements such as multilayer mirrors, which we have been developing in-house, to next-generation semiconductor lithography systems and soft X-ray microscopes.