Fine dispersion or full exfoliation of nanoparticles in matrix is one of the most important factors to achieve high performance polymer nanocomposites.In this talk, mechanically robust, magnetic nylon-6 nanocomposites reinforced by 1D carbon nanotube (CNT)-2D clay nanoplatelet hybrids have been prepared using simple melt-compounding technique.The direct iron-catalyzed chemical vapor deposition growth of multi-walled carbon nanotubes utilizes iron oxide-immobilized clay nanoplatelets as substrates, carrying out in-situ intercalation and exfoliation of clay nanoplatelets [1].By using such hybridization and co-exfoliation method, the as-obtained heterostructured hybrids used without any purification are demonstrated to be ideal and excellent nanofillers for mechanical reinforcement for fabricating nylon-6 nanocomposites, due to their homogeneous dispersion and strong interfacial interaction with the polymer matrix.The nucleation sites provided by the nanohybrids seem to be favorable to the formation of thermodynamically stable α-phase crystals of nylon-6 with much higher stiffness and hardness than γ-form of nylon-6, namely, a silicate-induced crystal transformation from the α-form to the γ-form of nylon-6 was greatly inhibited or "shielded" by the CNTs wrapped clay nanoplatelets.Furthermore, the nanostructured CNT-clay hybrid heterostructures containing residual iron oxide nanoparticles show novel magnetic properties either in bulk solids or in polymer nanocomposites [2].Therefore, this can be probably developed into a facile and practical method to fabricate polymer nanocomposites with high performance and multi-functionality.