The　preparation　of　3D　functional　isolated　mesoscopic　assemblies　remains　a　challenge　in　the　self-assembly　of　polymers.　Here,　well-defined　3D　hexagonal　and　hexagram　prisms　with　uniform　dimensions　are　acquired　by　the　crystallization　of　the　inclusion　complex　composed　of　a　crystalline　molecule　tris-o-phenylenedioxycyclotriphosphazene　(TPP)　and　a　block　copolymer.　The　crystalline　TPP　plays　an　important　role　in　the　self-assembling　process.　The　faceted　morphologies　of　the　hexagonal　and　hexagram　prisms　are　infrequent　in　the　self-assembly　field　of　soft　materials.　The　formation　of　the　prisms　experiences　a　3D　growth　mechanism.　The　epitaxial　growth,　accompanied　by　the　heterogeneous　nucleation　in　the　edges,　yields　the　growth　of　inclusion　crystals.　This　study　provides　a　path　to　construct　well-defined　polymeric　soft　materials　with　broad　utility　based　on　numerous　supramolecular　complexes.　©　2021　Wiley-VCH　GmbH