This chapter contains sections titled: Introduction Polymer Lamellar Material Nanocomposites Types of Lamellar Nano-additives Montmorillonite Layer Structure Modification of Clay Nanostructures and Characterization X-ray Diffraction and Transmission Electron Microscopy to Probe Morphology Other Techniques to Probe Morphology Preparation of Polymer-clay Nanocomposites Solution Mixing Polymerization Melt Compounding Polymer-graphite and Polymer Layered Double Hydroxide Nanocomposites Nanocomposites Based on Layered Double Hydroxides and Salts Properties of Polymer Nanocomposites Potential Applications Conclusion and Prospects for the Future