This thesis gives an overview of existing information on natural aging and clustering in aluminum alloys. An in-depth understanding of existing analysis methods of clustering is established. Moreover, an approach is developed, and applied, to access natural aging times below one hour via atom probe tomography. With the realized experiments it is shown that the as-quenched state can be investigated. Moreover it is demonstrated that clustering and all non-equilibrium vacancy controlled diffusionional processes are size-dependent and natural aging is effectively stopped when the material dimensions reach the nanometer scale.