The zinc-ion battery is one of the promising candidates for next-generation energy storage devices beyond lithium technology due to the earth abundance of Zn materials and their high volumetric energy density (5855 mA h cm-3). To date, the formation of Zn dendrites during charge-discharge cycling still hinders practical application. It is, therefore, crucial to understand the formation mechanism of the zinc dendritic structure before effectively suppressing its growth. Here, the application of operando digital optical...