There is growing evidence that liquids behave differently within nanometer-proximity to surfaces due to the formation of quasi-ordered "interphase." Understanding the correlation between the surface chemistry, the interphase structure and the resulting in terfacial forces between neighboring surfaces is of fundamental importance to various aspects of nano-scale materials research, including biomaterials, nanotribology and microelectromechanical (MEMs) devices. We use interfacial force microscopy (IFM) to q uantitatively measure interfacial bonding and frictional forces in order to identify the correlation between surface chemistry and interphase sturcture. We outline the results from two systems. In the first, we measure forces between a gold tip and sample, both coated with oligo(ethylene glycol)-terminated SAMs, in water. We observe anomalous interfacial forces due to the interphase water layer, which dominates the interfacial properties. It has been suggested that the interphase water is responsible for the protein-resistant nature of this SAM surface. In the second, we use a long-chain hydrocarbon liquid, hexadecane, which is known to form an ordered layer on a flat metal surface (e.g., gold). We find that this ordered layer passivates the interfacial i nteraction of a tungsten tip with a gold surface even under high stresses. The structure of this layer can be perturbed by applying an electric field and results in extended frictional forces without significant changes in the behavior of the normal-force. These results will be discussed in terms of the interfacial chemistry and the structure of the interphase liquid. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under a Contract DE-AC04-94AL85000.H. H.