A series of events has revolutionized the research on semiconductor interfaces. One of the most interesting is the discovery that heterojunction band lineups can be modified by manipulating the interface on an atomic scale. Specifically, it has been possible to modify heterojunction valence band discontinuities by inserting ultrathin intralayers and to create homojunction band discontinuities by inserting double atomic layers. These successes also have an impact on the fundamental understanding of the interface parameters. In parallel, progress has been made in the understanding of Schottky barriers by studying silicon and germanium films on metal substrates; these experiments have clarified the relative role of the local chemistry and morphology in determining the barrier height. Additional, exciting possibilities are opened up by the advent of lateral resolution in some of the techniques, like photoemission, that are most extensively used in semiconductor interface research: this makes it possible to study the lateral dependence of the interface parameters, a problem that has been largely ignored in the past.