Electrocatalysis stands as the cornerstone discipline to deliver breakthroughs in electrochemical energy conversion technologies, including fuel cells as well as carbon dioxide reduction, nitrate reduction and water splitting electrolysers. Nevertheless, crucial electrocatalytic reactions grapple with sluggish kinetics and inadequate selectivity. A fundamental understanding of reaction mechanisms and factors that limit activity and selectivity towards targeted products is imperative in order to prompt progress in electrocatalyst design and development. However, these endeavors are complicated and hindered by the intricate multistep mechanisms and concurrent interrelated factors arising on multiple scales. Figure depicts four essential components of a comprehensive understanding of electrocatalytic reactions: