Functionalization with a shell of covalently bound molecules is a common strategy for designing the surface features of colloidal nanomaterials. The functionalizing shell can assure colloidal stability or mediate the self-assembly behavior to form aggregates with controlled shapes . The ligands on the NP surface can mediate NP-NP interactions by different means: simple Coulomb forces for charged ligands , hydrogen bonds , dipole-dipole interactions , DNA base pairing interactions , and hydrophobic interactions . The broad freedom of choice of functionalizing agents, and the possibility to vary their density and heterogeneity, imply that the NP assembly processes can be very diverse. If a single ligand type functionalizes the surface of the NP, it can mediate NP-NP interactions, while the resulting superlattice structure will be mainly driven by the NP shape . Using two or more functionalizing molecules can provide the NP with Janus patchiness , tetravalent directional bonding that can lead to colloidal crystal assembly , and facet-specific functionalities that can drive the assembly into rods or planar aggregates Throughout this vast corpus of literature, the growth of anisotropic NP assemblies results from either anisotropic core shape or surface patchiness, or both. An interesting exception to this general trend was represented by silica nanoparticles functionalized by a thick, soft and hydrophobic polystyrene (PS) shell that, despite the random surface arrangement of the PS chains, were found to aggregate anisotropically, forming different structures depending on the PS surface grafting density. Anisotropy was shown to emerge from the entropy-enthalpy balance resulting from the deformation of the soft shell of neighbor NPs within the aggregates.