In this contribution, we share a few recent examples where in situ analytical techniques have advanced our understanding of structure-activity relationships of electrocatalysts and electrocatalytic reactions. Special emphasis will be placed on synchrotron-based X-ray techniques, new approaches in electrochemical mass spectrometry, and in-situ electrochemical transmission electron microscopy. Reactions of interests include the oxygen reduction reaction on Pt based and carbon based catalysts, the oxygen evolution reaction on CoOx and NiFeOx, as well as the electroreduction of CO₂.