The Advancing Frontier in the Knowledge of the Structure of Interphases.- Some Recent Spectroscopic Approaches to the Solid-Solution Interface.- Application to Electrocatalysis of EMIRS (Electrochemically Modulated Infrared Reflectance Spectroscopy) and Related Techniques.- Photoacoustic Spectroscopy and the In-Situ Characterization of the Electrochemical Interface.- Raman Spectroscopic Techniques in Interfacial Electrochemistry.- Laser Raman Spectroscopy in Studies of Corrosion and Electrocatalysis.- UV-Visible Reflectance Spectroscopy in Electrochemistry.- Study of Anodic Oxides by UV-Visible Potential-Modulated Reflectance Spectroscopy.- Nonlinear Optical Techniques for Surface Studies.- X-Ray Diffraction at the Electrode-Solution Interface.- X-Ray Reflectivity and Surface Roughness.- Surface Structural Investigations by Electron Diffraction Techniques.- Auger Electron Spectroscopy and the Electrochemical Interface.- Photoelectron Spectroscopy (XPS and UPS) of Electrode Surfaces.- Rutherford Backscattering Spectroscopy of Electrode Surfaces.- Electrochemical Applications of Scanning Tunneling Microscopy.