showing a H C of 250 Oe. The high concentration of interfaces in the nanocomposites further allows to take advantage of different magnetic phases in order to fine-tune the magnetic behavior. As can be seen in the SI Fig. , the M S and H C varies between 40.5-50.8 emu g -1 and 3.0-75 Oe, respectively, depending on the treatment of the SPs. Moreover, ferrimagnetic materials typically exhibit a small gradual increase in their magnetic moment at high fields before reaching their saturation magnetization due to remaining antiparallel aligned moments. The magnetization slope, s unsat , at 10 kOe can be modified between 33.6-58.9 emu g -1 kOe -1 depending on the interface modification. In addition, small fractions of a different magnetic phase were observed depending on the used amine-ligand, as evidenced by stepped features in their hysteresis curves. This effect was more significant when a thiol-derived ligand was used (Fig. , inset) again indicating structural changes at the supercrystalline surfaces which can be controlled by the processing conditions. decreased due to the crosslinking reaction. In addition, the composite materials have a quite low density of 2.6 g cm -3 compared to commonly used magnetic materials reaching ∼ 7 g cm -3 (e.g. soft iron or neodymium). Combined with the achieved high magnetization of the nanocomposites, the material is susceptible to be manipulated with an applied magnetic field as demonstrated in Fig. and therefore emerges as an ideal candidate for magnetic actuation e.g. in microrobotic applications. Conclusions A nature-inspired, multiscale material design for the fabrication of robust, macroscale nanocomposites with tunable functional properties is presented. The material shows high bending strength and fracture toughness due to a multi-hierarchical arrangement of self-similar, hard filler particles connected via soft organic interfaces. A high filler content of the inorganic component and its preserved nanostructure allows to efficiently foster its nano-functional properties. The developed nanocomposites show tunable magnetic behavior with a high saturation magnetization, low magnetic coercivity, low density, high electric resistivity, and easily adjustable macroscopic shape. The design strategy exploits abundant reagents and versatile synthetic steps which are adaptable to other desired starting materials. Ultimately, these composites' combination of macroscopic size, mechanical integrity, and nano-functional properties paves the way towards implementing nanomaterials into serviceable, macroscale, engineering components.