Many of the most important properties of materials in high-technology applications are strongly influenced or even controlled by the presence of solid interfaces. In this work, leading international authorities review the broad range of subjects in this field focusing on the atomic level properties of solid interfaces.Contributors. Introduction. Atomic-level geometry of crystalline interfaces; D. Wolf. Experimental investigation of internal interfaces in solids; D.N. Seidman. Bulk interfaces. Part I: Bulk interfaces. Correlation between the structure and energy of grain boundaries in metals; D. Wolf, K.L. Merkle. Grain and interphase boundaries in ceramics and ceramic composites; M.G. Norton, C.B. Carter. Special properties of E grain boundaries; G. Palumbo, K.T. Aust. Grain boundary structure and migration; D.A. Smith. Role of interfaces in melting and solid-state amorphization; S.R. Phillpot, S. Yip, P.R.Okamoto, D. Wolf. Wetting of surfaces and grain boundaries; D.R.Clarke, M. Gee.Part II: Semi-bulk and thin-film interfaces. Structural, electronic and magnetic properties of thin films and superlattices; A. Continenza, C.Li, A.J. Freeman. Surfaces and interfaces as studied by scanning-tunneling microscopy; R. Hamers. Epitaxy of semiconductor thin films; J. Batstone. Phase behavior of monolayers; S.G.J. Mochrie, D. Gibbs, D.M. Zehner. Elastic and structural properties of superlattices; M. Grimsditch, I.K. Schuller. Computer simulation of the elastic behavior of interface materials; D.Wolf, J. Jasczak. Interfaces within intercalló%