The synergistic interaction of different components in heteronanocrystals induces interfacial phenomena and novel functionalities. Nonetheless, effective technologies to design and fabricate heteronanocrystals with materials on demand are still missing. Rich heterostructures in a copper patina are known to form at room temperature and under atmospheric pressure. The redox process of copper tarnish inspired the discovery of a simple strategy to achieve heteronanocrystals that contained elements from group 3–11 and group 14–16. The interface redox-induced method is self-regulating at ambient conditions and applicable for metal, semiconductor, and dielectric materials. The enhanced interface bonding endows the heteronanocrystals with outstanding stability and catalytic performance, while the modular approach enables the design and fabrication of heteronanocrystals with intended materials to meet different purposes.