Probing inside a material, at the interface of two different layers, is one thing. Doing this under realistic circumstances, while the materials are active, is another, and it is not so easy. That is exactly what researchers of the MESA+ Institute of the University of Twente would like to achieve, using the special machine they are building. Thanks to a three-‘colour’ X-ray system, they will be able to look at three separate depths. The machine, for which Dutch Research Council NWO granted a large subsidy, will prove its unique qualities in, for example, the development of new types of batteries for electric mobility and new catalysts for producing green hydrogen.