Ternary twinned Zn2TiO4 spinel nanowires are formed by a solid-state reaction between Ti and ZnO from an amorphous Ti-coated ZnO core/shell nanowire structure. The ZnO nanowires are used as templates to spatially confine the formation of Zn2TiO4 nanowires. TEM investigations (see figure) reveal the nature of both the ZnO/Ti core/shell structure and the < 111 >-oriented growth of the twinned spinel nanowires.