Understanding the structure-reactivity relationship at electrochemical interfaces is central to unraveling nearly all electrochemical processes, including electrocatalysis and batteries. However, these interfaces are typically structurally heterogeneous, which impedes interpreting the structure-activity relationships using conventional ensemble electrochemical measurements. In this presentation, I will discuss our efforts toward developing and applying electroanalytical techniques—such as scanning electrochemical probe microscopy and correlative microscopy—to gain new knowledge from electrochemical interfacial heterogeneity. First, I will discuss our efforts towards simultaneous probing of local activity and product selectivity in electrocatalytic reactions via a hybrid scanning electrochemical probe microscopy approach, equivalent to a miniature rotating ring disk electrode. Combined with correlative electron microscopy, this approach enables simultaneous mapping of the facet-dependent activity and selectivity in the oxygen reduction reaction (ORR) on polycrystalline Au and Pt. In the second example, I will discuss the approach to measure site-specific nucleation kinetics and energetics in electrodeposition, which plays an important role in the cyclability of batteries that use metal anodes. Finally, the application of controlled electrodeposition towards accelerated materials discovery will be discussed.