Multilayered alternating film/foam structures are fabricated using the Micro/Nano-layered (MNL) coextrusion technology. By varying the individual layer thickness and the number of film/foam interfaces in such multilayered structures, the resulted cell sizes, cell densities, and cell size distributions are greatly affected by the layer thickness and film/foam interfaces. As the layer thickness of the foam layers are decreased, the cell growth in foam layers is confined by the adjacent films, resulting in confined cell growth and smaller cell sizes. The cell nucleation is promoted by the interfaces between film layers and foam layers. Consequently, higher cell densities are observed in multilayered film/foam samples with more interfaces. The adjacent film layers can also act as physical barriers to prevent cell coalescence and gas loss during the foaming process, preserving more nucleated cells. Therefore, advanced film/foam multilayered structures with higher cell densities, more uniform cells, and smaller cells can be fabricated using this MNL coextrusion technology.