With the looming global environmental crisis, electrochemical CO2 reduction (CO2R) is a hot topic. Excellent perspectives on mechanistic studies1-3 practical vapor-fed devices4, and technoeconomic and system-level analyses5-7 have come out in the past few years, all with compelling visions for the future. We can also harken back to Hori’s timeless review of his work over several decades8, which seeded many of the impressive advances today. But as the French maxim says: parfois, il faut reculer pour mieux sauter. Here, I showcase a few basic concepts in the fundamental mechanistic studies of CO2R.