It is essential to model and simulate the changes in shape and structure of polymer blends at the nanoscale that do not mix well during the process of injection molding. This is important for accurately forecasting and adjusting the performance of the final products. This chapter examines the latest advancements in the modeling and simulation of injection molding of polymer blends at many scales. A comprehensive assessment was conducted on the technological advancements in macroscale injection molding simulation. The discussion focused on several models that explain the evolution of morphology at a mesoscale level during the process of injection molding. An analysis and comparison were conducted on the existing strategies that bridge the gap between macroscopic mold-filling flow and mesoscopic morphological evolution. The advantages and disadvantages of these solutions were also examined. Ultimately, a thorough overview of the aforementioned models is provided, along with the prospects for future investigation in this domain.