It was noted that, using established methods of diffusivity measurement, it was possible to measure diffusion processes only at length-scales down to 10nm; with corresponding diffusivities of 10−23m2/s. However, for complex materials such as amorphous or nano-structured solids, the given values were often not sufficient and it was necessary to detect diffusion lengths which were well below 1nm. The method of neutron reflectometry on isotope multi-layers was presented here. For two model systems (amorphous semiconductor, amorphous metallic alloy), the efficiency of this method was shown to lead to the detection of minimum diffusion lengths of only 0.6 to 0.7nm. It was further shown that diffusivities could be derived which were more than two orders of magnitude lower than those obtainable using conventional methods. How to Measure Atomic Diffusion Processes in the Sub-Nanometer Range. H.Schmidt, M.Gupta, T.Gutberlet, J.Stahn, M.Bruns: Acta Materialia, 2008, 56[3], 464-70