Hybrid nanostructures present a catalog of promising functional materials with a broad range of applications. Structural control has been proved versatile to optimize functions and properties of the nanomaterials. Although polymer/inorganic hybrid nanoparticles have been achieved through selfassembly of block copolymers, synthesis of hybrid nanoparticles with small size (≤20 nm) remains challenging. Herein, we developed a conceptually new approach for efficient and scalable synthesis of 10 polymer/inorganic hybrid nanoparticles with well-defined shape and tiny size through direct disassemblyassisted synthesis (DDAS) strategy. Incorporating cyanoferrate into polypeptides led to disassembly of large hexagonally-packed structures of polypeptide α-helices into small aggregates. Subsequent coordination polymerization of the cyanoferrate groups with Fe 3+ in aqueous media afforded polypeptide/Prussian blue (PB) hybrid nanoparticles with well-defined core-shell structures. Hybrid 15 nanoparticles were thoroughly characterized. Morphological and microstructural analyses showed that the hybrid nanoparticles had small size of approximately 18 nm and crystalline PB phase. Taking advantage of tiny size and crystalline PB phase, the hybrid nanoparticles showed excellent electrocatalytic activity toward reduction of hydrogen peroxide. Such direct disassembly-assisted synthesis of polymer/inorganic tiny nanoparticles provides a family of functional nanomaterials useful for biosensing and nanodevice 20 applications. 65 spheres were achieved by means of direct assembly of goldcontaining block copolymers. 34,35 Recently, tiny nanoparticles with small size have received particular interests, because the surface area of nanoparticles A conceptually new approach for synthesis of tiny hybrid nanoparticles through direct disassembly-assisted synthesis (DDAS) strategy has been developed.