While retaining the same 4-arm topology shown in Fig. , we vary nanostar arm length l between 21 and 51 base-pairs (bp). l is controlled by changing the length of the core-forming strands while keeping that of the cholesterolized strand fixed, as shown in Fig. . Correct folding of individual nanostar motifs was confirmed by Agarose Gel Electrophoresis (AGE) and Dynamic Light Scattering (DLS), using soluble building blocks in which the cholesterol-modified strands were replaced by non-functionalized ones of identical sequence. AGE produces single sharp bands for arm lengths of 24-51 bp, while nanostructures with l = 21 give rise to a more smeared band, indicating that such small junctions are not individually stable in running buffer (see Fig. in SI). Fig. demonstrates how the relative electrophoretic migration distance R f decreases linearly with l in the range 24-51 bp, deviating for l = 21 bp. A consistent trend is observed in the mean hydrodynamic diameter D h measured by DLS, increasing with l. For C-star samples with l = 21-42 bp we observe the formation of equilibrium single crystals that, irrespective of arm length, feature a rhombic dodecahedral geometry consistent with an underlying cubic symmetry (Fig. , left). The relationship between the C-star arm length and the microscopic structure of the self-assembled aggregates was investigated by Small Angle X-ray Scattering (SAXS). Diffraction profiles obtained from "powder" samples, featuring dense packings of individual crystals demonstrate that all C-star samples exhibiting polyhedral aggregates adopt a body centredcubic (BCC) unit cell (Fig. , centre and right). Consistent with a crystal geometry independent on arm length, the measured lattice parameter a increases linearly with l, matching very closely the predicted value a t (Fig. ). We estimate a t through a simple geometrical model, where C-star arms are modelled as rigid rods of length equal to d bp l (d bp = 3.4 Å/bp) and the cholesterol-rich cores are approximated to spheres of radius r mici = 30.3 Å, in very good agreement with the previously estimated value for l = 28 C-stars 32