Energy storage is the missing enabler to facilitate the widespread installation of renewable-but-intermittent solar and wind energy. There are two primary metrics for stationary energy storage: cost and cycling life, where the latter is also about the cost, indeed. It is thus a must to rely on Earth-abundant elements, which rules out lithium-based devices for the stationary purposes, as lithium is rare and its supply is geopolitically challenged. This warrants attention for Na-ion batteries (NIBs) and K-ion batteries (KIBs). For metal-ion batteries, the choice of anode often determines the fate of the battery commercialization, as anode typically determines battery’s cycling life as well as safety features. Considering the cost and performance, non-graphitic carbon anodes are the leading candidates for NIBs and KIBs. To date, much effort has been devoted to preparing such carbons from various unique organic precursors. However, there has been a dearth of knowledge on the basic correlation between the local structures of carbon anodes and their Na (K)-ion storage behavior, where the alkali-metal-cation storage mechanism in hard carbon and soft carbon is still a debated topic. In this talk, I will introduce new insights on storage mechanisms and design principles of hard carbon anodes for NIBs based on the structure-capacity correlation revealed by experimental and theoretical studies. I will also discuss K-ion storage properties of major carbons, including graphite, which proves incorrect an old assumption between graphite and potassium.