Bioinspired composites exhibit well-defined microstructures, where anisotropic ceramic particles are assembled and bonded by an organic matrix. However, it is difficult to fabricate these composites where both the ceramic particles and organic matrix work together to unlock toughening mechanisms that lead to stiff, strong, and tough mechanical properties. Here, we produce composites inspired by seashells, made of alumina microplatelets assembled in complex microstructures and are physically bonded by a small amount of interpenetrating polymer network (IPN) consisting of poly(N-isopropylacrylamide-co-acrylamide) and polyvinylpyrrolidone (PVP). The fabrication employs magnetically assisted slip-casting to orient the microplatelets as desired, and in situ gelation of the IPN, followed by drying. The process was successful after carefully tuning the casting and gelation kinetics. Samples with horizontal, vertical, and alternating vertical and horizontal microplatelets orientations were then tested under compression. It was found that the IPN threads bonding the microplatelets acted as sacrificial bonds dissipating energy during the compression. Paired with the alternating microstructure, the IPN significantly enhanced the compressive toughness of the composites by 205% as compared to composites with horizontal or vertical orientation only, and less than 35% reduction on the stiffness. This study demonstrates that microstructure control and design combined with a flexible and tough matrix can effectively enhance the properties of bioinspired ceramic polymer composites. Further research on the microstructured alumina-IPN composites in dry and hydrated states or varying different parameters (e.g., ratio between the hard and soft IPN-forming components, amount of crosslinker used, etc.) could unlock toughening mechanisms to generate bioinspired composites with outstanding mechanical properties and biocompatibility. [1]