Until the mid 1980s, there had been only a few in situ methods available for the atomic level structural determination of electrode surfaces in solution. Now several investigations have demonstrated that electrochemical scanning tunneling microscopy (EC-STM) is a powerful technique for in situ characterization, with atomic resolution, of surfaces under potential control. The object of this article is to highlight some of the advances in in situ scanning tunneling microscopy (STM) with atomic resolution. Several selected topics, observation of clean platinum electrode surface, specifically adsorbed anions such as iodine and sulfate on metal surfaces, adsorption of porphyrin on clean and iodine-modified electrodes, and binary adlayer consisting of porphyrin and phthalocyanine on gold electrode are focused on.