Isotactic polypropylene (iPP) has experienced a massive volume growth since its introduction in the mid-1950s and is nowadays present in an extremely wide range of applications. One of the essential reasons for this development is the flexibility of this polymer in terms of property design and processability. The polymorphism of iPP, i.e. its capability to solidify in so far five documented crystal modifications from ¦Á to ¦Å [1-3] and in a mesomorphic state [4] is one key element of this flexibility. In our presentation we will demonstrate ways of combining polymer design, nucleating agents and processing pathways to utilize polymorphism for fulfilling specific application requirements. Several quite diverse applications like car bumpers, hot-water pressure pipes, cast and biaxially oriented (BOPP) film and sterilisable medical pouches all can benefit from this crystallinity based design. Basic research on iPP crystallization is elementary for achieving the target, as a thorough understanding is required to find suitable combinations of polymer composition, nucleation and process settings. References: 1 ¨C Br¨¹ckner S., Meille S.V., Petraccone V., Pirozzi B., Polymorphism in Isotactic Polypropylene, Prog.Polym.Sci. 16 (1991) 361-404 2 ¨C De Rosa C., Auriemma F., Vollaro P., Resconi L., Guidotti S., Camurati I., Crystallization Behavior of Propylene-Butene Copolymers: The Trigonal Form of Isotactic Polypropylene and Form I of Isotactic Poly(1-Butene), Macromolecules 44 (2011) 540-549 3 ¨C Lotz B., A New ¦Å Crystal Modification Found in Stereodefective Isotactic Polypropylene Samples, Macromolecules 47 (2014) 7612-7624 4 ¨C Androsch R., Di Lorenzo M.L., Schick C., Wunderlich B., Mesophases in polyethylene, polypropylene, and poly(1-butene), Polymer 51 (2010) 4639-4662