Hierarchical heteronanostructures of W nanothorns On WO3 nanowhiskers, as shown in the figure, was fabricated with a simple two-step thermal-evaporation process. A high density of W nanothorns form a heteronanostructure with thick WO3 nanowhiskers. A chemical transport-condensation model based on a vapor-solid mechanism is proposed for the formation of the W/WO3 hierarchical structures.