During the past decades, substantial effort has been devoted to developing new
experimental techniques capable of delivering atomic-scale information on supported nanoparticles under industrially relevant catalytic reaction conditions. Development of new in situ techniques both contributes to and is driven by the developments in catalysis.
The need to study catalysts at high temperatures and pressures in a reactive gas or liquid atmosphere resulted in the design and construction of in situ and operando reactors enabling structural characterization of catalysts under relevant reaction conditions down to the atomic scale. This is crucial for development of new and improved catalysts to support sustainability of natural resources, energy and the environment.
Synchrotron-based techniques are especially versatile for the study of catalysts under reaction conditions due to the high penetrating power of X-rays, the tunability of the Xray energies over a broad range and the possibility to collect data with a high temporal and spatial extent. Several relevant properties such as crystal structure, elemental composition, chemical state, bond distances, particle sizes and size distributions, phase composition and the structure of the pore system can be studied by synchrotron-based techniques. Pore characterization is of crucial importance for heterogeneous catalysts,
because the reactants and products have to be able to enter and exit the catalytic active sites present within the pores. Also, electron-microscopy-based techniques have continued to improve significantly during the last many years. Recently, we have shown that it is even possible to obtain atomic-scale information of catalysts during operation at high temperatures and pressures above ambient.

In this contribution I will give examples of the industrial use of various synchrotronbased and transmission electron microscopy-based techniques for the understanding and development of industrial catalysts. Examples in the areas of hydrotreating catalysis and
methanol synthesis will be shown to illustrate the changes from trial and error-based design of catalysts, via in situ studies, to a knowledge-based design of supported catalysts.