UNISA code, a software for the analysis and modeling of injection molding, was born at the University of Palermo in Italy in the 1980s. Afterwards, in the 1990s, it was rewritten and expanded at the University of Salerno (Italy) and continuously improved over the years. It is a study code, aimed at understanding rather than simulating. It has the unique characteristic of describing, since the early versions, the morphology of the molded samples. Furthermore, it always implemented the interrelationships among the different material properties (crystallinity, viscosity, density). In this work, the evolution of the software is reviewed, placed in the background, underlining the contribution given to the understanding of polymer processing and morphology evolution. Eventually, the future challenges of modeling are presented.