With the capability of direct visualizing the solid–liquid reactions at high resolutions, in situ liquid-cell transmission electron microscopy (TEM) plays an important role in the fundamental studies of rechargeable batteries, including the lithiation behavior of various electrode materials, the striping/plating behavior of lithium metal anode, the formation of solid–electrolyte interfaces, electrolyte degradation behaviors, as well as the formation/dissolution behavior of Li₂O₂/NaO₂ in the metal–air battery cathode. This article summarized the recent progress of in situ electrochemical-cell TEM technique in the battery field by comparing its advantages/disadvantages with traditional open-cell TEM technique as well as other in situ techniques. With the improvement of the chemical analysis capabilities and new holder designs, in situ liquid-cell TEM will see further applications in battery systems beyond lithium-ion.