This chapter aims to provide recent advancements in manufacturing, crystallization characteristics, and structural characterization of nanoclay-containing polymer (nano)composites. The study of diverse polymer composite materials has changed dramatically with the introduction of nanoclay-containing polymer nanocomposites (PNCs) with at least one filler dimension less than 100 nm; these materials are hybrid nanocomposites of organic and inorganic components. Many synthetic techniques have been revealed to produce these materials. These techniques include intercalation/exfoliation of polymers or pre-polymers from liquids, melt intercalation/compounding, in-situ polymerization, and more. Because of the special filler surface modifications, the nanoclay platelets are dispersed within the polymer matrix at the nanoscale, greatly improving the properties of PNCs, such as enhanced mechanical strength, gas barrier, thermal stability, flame retardancy, and others. As a result of the improvement in properties, NC is usually only needed in small amounts, allowing the composite materials to keep their low density and transparency with respect to their virgin form.