Cu-Nb-0.18 (%vol.) composite wires and pearlitic steel wires (steel\backslashncord) were produced by cold drawing. The high level of plastic\backslashndeformation leads to the formation of nanostructured materials through\backslashngrain refinement. These two kinds of wires were investigated using 3D\backslashnAtom-Probe and Transmission Electron Microscopy (TEM) to exhibit their\backslashnnanoscaled structure. Experimental data on steel cords revealed the\backslashndissolution of cementite lamellae which thickness was reduced down to a\backslashnfew nanometres during drawing. The microstructure of Cu/Nb wires was\backslashnalso mapped out in 3D. Nanoscale Nb fibres and Cu channels with smooth\backslashnCu/Nb interfaces attributed to stress-induced diffusion were exhibited.\backslashnThese new experimental results give rise to new arguments to account\backslashnfor the enhanced mechanical properties of cold drawn pearlitic steel\backslashnwires and Cu/Nb nanocomposite wires.