Some of the significant issues associated with the field of polymer nanocomposites (PNC), with specific focus on the opportunities in which theory, modeling, and computer simulations from polymer physics will help in realizing the potential of PNC, are discussed. It has been observed that many of the nanofillers used in PNCs are characterized by strong van der waals interaction particles, which promote their agglomeration. The effective interactions between these nanofillers are also influenced by the polymer-filler interactions, leading conditions that are suitable to the aggregation of the fillers. It has been found that aggregation and clustering of the fillers leads to a significant reduction in the interfacial contact between the fillers and the polymer. These interactions between the fillers and the polymer results in deterioration of the property enhancements that can be attained in PNCs.