Most of the attempts to tailor the surface reactivity have focused on the creation of specific surface structures, where electronic perturbations are induced, or by chemical modification of the surface properties by adding small amounts of substances. Recently it has been shown that the chemical specific imaging, combined with laterally resolved structural characterizations is of vital importance for understanding key factors controlling the processes at the surface of complex systems and the related to that local reactivity. In the talk selected results obtained using chemical specific imaging, photoelectron micro-spectroscopy, low energy electron microscopy and scanning tunnelling microscopy will be presented and discussed. The effect of electron confinement in ultrathin films will be illustrated for Mg films with varying thickness at micrometer scales; they show sensible difference in the local oxidation rate, correlated to the periodic changes in the density of electronic states induced by quantum-well states crossing the Fermi level of the Mg film.@footnote 1@ The complexity of the realistic systems, where a rich variety of self-organized micro and/or nano-structures may form and coexist under reaction reactions will be illustrated using the results obtained with Rh surfaces modified with potassium or other metals.@footnote 2,3@. In will be shown that stabilization of the substrate surface reconstructions and mass transport driven self-reorganization processes are common phenomena, which may affect the composition and reactive properties of the surface at local microscopic scales. @FootnoteText@@footnote 1@ L. Aballe et al, Phys. Rev. Lett. 93, 2004, 196103. @footnote 2@ S. G@um u@nther et al, J.Chem. Phys. 117, 2002, 2923119; ibid. 119, 2003, 12503; J. Phys. Chem. 2005, in press. @footnote 3@ A. Locatelli et al, J. Am. Chem. Soc. 127, 2005, 2351.