Interfacial systems are frequently encountered in a large variety of phenomena in biology and industry. A few examples that come to mind are adsorption, catalysis, corrosion, flotation, osmosis, and colloidal stability. In particular, surface films are very interesting from a cognitive point of view. Surface science has a long history. For many years, natural philosophers were curious about interfacial phenomena because it was quite clear that matter near surface differs in its properties from the same matter in bulk.