Electrochemical scanning tunneling microscopy (EC-STM) was employed to examine the molecular assembly and electropolymerization processes of 3,4-ethylenedioxythiophene (EDOT) onto reconstructed and unreconstructed Au(1 0 0) single crystal electrodes in a 0.1 M HClO4 electrolyte solution. The EDOT adsorption onto the Au(1 0 0)-hex surface induced lifting of the reconstruction at potentials as low as E = 0.150 V (vs. reversible hydrogen electrode (RHE)), which is clear evidence of the strong EDOT-Au interaction that was also observed by cyclic voltammetry (CV). EC-STM was also able to reveal, for the first time, the dynamic process of EDOT molecular self-assembly onto the Au(1 0 0)-(1 x 1) surface. The EDOT adlayer was found to fit into a 4 root 2 x 3 root 2 unit cell. High-resolution STM imaging revealed a vertically tilted geometry for the EDOT molecules. Electropolymerization was also performed, revealing the solution-process formation of polymer bundles. (C) 2012 Elsevier Ltd. All rights reserved.