This paper presents fundamental studies and observations of the adhesion, friction, deformation, and fracture behavior of solid surfaces undergoing solid-to-solid contact and liquid-to-solid contact. Emphasis is on the basic material and structural characteristics, as well as the surface effects, in the tribological phenomena. First, the adhesion and friction behaviors of smooth, atomically clean surfaces of solid-solid couples in a clean environment are presented, and the friction mechanisms are described in terms of surface energy and ductility. The roles of interface species (dispersed carbon nanotubes as well as contaminant and oxide layers) are also considered. The importance of surface analytical techniques used both to understand the phenomena and mechanisms of adhesion, friction, deformation, and fracture and to define the associated problems is addressed. Secondly, deformation behavior of single crystals, such as MgO, subjected to hardness indentation and cavitation erosion is discussed. How the deformation behavior relates to crystal orientation and distribution of dislocations is explained. Thirdly, crack patterns in ceramics, such as diamond, generated by spherical indenters under normal loading are discussed in relation to the structures, impurities, and properties of the ceramics.