Solid catalysts are crucial enables of today's chemical industry and the key towards a green society in the coming decades. However, the properties of these nanomaterials under true working conditions remain elusive to date, but govern the catalyst performance. A primary focus has been to characterize the structure of solid catalysts, but in many cases metrology of their structural features has not been performed under relevant reaction conditions and remains incomplete, hence not detailing the true nature of the active site. In addition, yet-untapped but equally important catalyst properties, such as the catalyst temperature, have been largely disregarded due to characterization challenges. In this project, advanced characterization tools will be explored in combination with the development of novel catalyst design concepts to chart and exploit to date-elusive properties of novel working catalysts.