Comprehensive models for the injection molding process have been proposed in the last forty years taking into account the simultaneous flow and heat transfer that occurs during the filling, compression and cooling stages. The combination of melt flow and heat transfer, during the injection molding process, has the decisive effect on the structuring and properties of molded products. In the case of high aspect ratio micro-fibers and nano-fillers the structure evolution and derived properties of injection molded products are governed by the orientation development of the polymers themselves and the high aspect ratio species with simultaneous cooling. Theoretical modeling of the orientation build up was the starting stage for studying the evolving structure followed by experimental investigation comprising optical and electronic microscopy and supplemented by mechanical properties characterization. The modeling and experimental results have shown that the elongational and shear flows with simultaneous cooling cause the formation of as layered structure. The relative size of the resulting layers is determined by the heat transfer process that takes place during flow in the mold cavity. The paper will cover the structuring of liquid crystalline polymers (LCPs), short fiber glass and carbon polymer composites and finally nanoclay and carbon nanotubes containing polymers.