Electrochemical activity of mechanically exfoliated graphene was mapped with high spatial resolution by scanning electrochemical cell microscopy (SECCM), using aqueous Ru(NH3)63+ as a redox probe [1,2]. In combination with electrochemical imaging data, the characterization of the graphene sample with atomic force microscopy (AFM), Raman spectroscopy, and optical microscopy revealed enhanced electron transfer (ET) kinetics along step edges and a gradual diminution of the ET rate from graphite to monolayer graphene (Fig. 1a and b). Surprisingly, but not all step edges demonstrated enhancement of ET kinetics, which is tentatively attributed to covering graphene layers that accidentally form during mechanical cleavage, thus, hiding some step edges from a direct contact with the electrochemical probe. Similarly, the said enhancement was found on step edges of highly oriented pyrolytic graphite (HOPG) when imaged with the same redox probe (Fig. 1c). However, imaging electrochemical activity of HOPG with two other redox couples (aqueous ferrocene derivatives) yielded an image of a uniformly active surface. With a modified version of SECCM, in which voltammetric measurements are run at each pixel of the image, we were able to record a potential-resolved movies of electrochemical activity of HOPG, which partially removed the veil from the observed step edge reactivity.   Superior reactivity of step edges was rationalized in view of the density of states (DOS) concept. The formal potential of Ru(NH3)63+ is very close to the Dirac point of undoped graphene where the DOS is very low (theoretically, zero), while the edge state exhibits a maximum in DOS at the same region of potential. As a consequence, ET kinetics of non-adiabatic electrochemical reactions should be affected by the marked difference in DOS, and, indeed, this was observed experimentally. On the contrary, the formal potentials of the ferrocene derivatives are located in the region of potential where the DOS for graphene’s basal plane and the edge state is not so dissimilar; hence, no difference is observed for these two couples at both the basal plane and step edges.