Several nanoanalytical techniques based on electron and atomic force microscopy were used to analyse the micromechanical deformation mechanisms in different nanostructured lamellae forming heterogeneous polymers: in ( semicrystalline) beta-modified isotactic polypropylenes and ( amorphous) lamellar styrene/butadiene block copolymers. It was found that the deformation processes in these two entirely different classes of materials are governed by fundamentally similar mechanisms due to similar dimension and arrangement of the nanostructures. The basic mechanism shows two steps: The initial step is determined by a plastic deformation of the soft ( amorphous or rubbery) phase with a reorganisation of the hard ( crystalline or glassy) lamellae and their orientation towards the deformation direction. The second step is characterised by the intense plastic deformation ( yielding) of the hard lamellae up to elongations of several 100%. (C) 2004 Kluwer Academic Publishers.