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Electronic correlation and electron-phonon coupling can cause Mott insulators or charge density waves, both phenomena significantly enhanced by the reduction of dimensionality. Correlated surfaces were discovered in the 1980s during studies aimed at understanding the microscopic details of Schottky barriers. In the Feature Article on pp. 614–626, Tejeda et al. show the relevance of semiconducting surfaces for the study of correlation effects. Evidence is provided that the narrow bands associated with widely spaced dangling bonds increase the electronic localization and may drive metal-insulator transitions. The localization can be tuned by studying similar reconstructions with different lattice parameters or different adsorbate species. For this purpose, the authors discuss the effects on K/Si(111):B and Sn/Ge(111) surfaces. Doping experiments with standard surface science techniques allow for further tailoring the systems and eventually relating the Mott insulators with two-dimensional superconductors. Furthermore, electronic localization is related to spin localization, which may promote exotic magnetic phases, especially in triangular lattice systems prone to magnetic frustration. This opens up new prospects for the future research on electronic correlation and many-body effects at surfaces.