It is shown that the Pd(1 1 1) and Au(1 1 1) surfaces with wide atomically flat terraces having widths in a range of 2-10 mu m can be prepared by annealing in an argon stream These surfaces were investigated by a laser confocal microscope combined with a differential interference contrast microscope (LCM-DIM) It is remarkable that regularly aligned step lines are clearly discerned in electrolyte solutions The step lines observed by LCM-DIM are monatomic steps confirmed by scanning tunneling microscopy and atomic force microscopy It is expected that LCM-DIM is a new powerful in situ method for the investigation of electrochemical reactions with the capability of atomic layer resolution (C) 2010 Elsevier B V All rights reserved