Understanding the forces such as adhesion, attraction, and repulsion between surfaces and liquids is the key not only to understanding phenomena such as lubrication and indentation but also the key to understanding how best to operate an atomic-force microscope (AFM). In this paper, we examined the cases of an insulating tip on an insulating sample (silicon nitride tip on mica) and of a conducting tip on a conducting sample (tungsten carbide tip on a gold or platinum foil). The force-versus-distance curves for these two limiting systems were very different in different liquids