Abstract <p>The phenomenology and nature of two-level (matrix and second phases) nanostructuring of complex aluminum alloys during thermomechanical processing based on cold severe plastic deformation are considered. The importance of taking into account the principle of structure heterogeneity optimization at all stages of processing by controlling the parameters of second phases is substantiated. A number of conclusions are formulated that can be used as the basis for the criteria of this principle for the alloy treatment involving severe plastic deformation to ensure its effective nanostructuring and property enhancement. A new approach to classification of nanostructured alloys is proposed.</p>