In this work, we give three examples of interfacial reactions in Al/transition metal (TM)- or Si/TM systems in which the specificities of the reactive diffusion (selectivity, nucleation threshold) on the nanoscale are emphasized. In particular, this allows the stabilisation of phases and interfaces, which are not expected from the equilibrium phase diagram, and a morphological development of the phases formed which can induce nanostructuring. (C) 2004 Elsevier B.V. All rights reserved.