Rational design of materials requires characterization during each step of their lifecycle, including under operating conditions. Notably, one of the key challenges arises from the fact that a small fraction of the material is involved in the catalytic events (few %). We thus employ and participate in the development of state -of-the-art spectroscopy and microscopy tools to interrogate these sites. Among various characterization techniques, we particularly like magnetic resonance approaches (EPR and NMR) as well as IR and X-ray adsorption spectroscopies. We also work on the development of probe molecules as well as on surface sensitive methods such as Dynamic Nuclear Polarization – Surface Enhanced Spectroscopy (DNP-SENS) and modulation approaches to highlight dynamic phenomena.