The concept of nanostructure is applied to catalysts for nitrogen oxide control and specifically in relation to the development of novel NOx storage-reduction (NOxSR) catalysts, as well as tuning metal particle size through metal-support interaction. In particular, the characteristics and reaction mechanism of Toyota-type NOxSR catalysts are examined. Control of the nanostructure makes it possible to design samples with improved performance based on hydrotalcite starting materials. In Rh-on-zirconia catalysts for N2O decomposition, the addition of small numbers of trivalent ions, inducing controlled oxygen vacancies in the zirconia support, allows the metal particle size to be tuned, thus promoting surface reactivity in N2O decomposition even in the presence of two or three orders of magnitude higher concentrations of O-2 with respect to N2O. The concept of controlling the nanostructure of the catalysts finds application in a wide range of situations of interest for catalytic technologies for environmental protection. (C) 2003 Elsevier Science (USA). All rights reserved.