Nanostructure-based leaf-like polyaniline (PANI) (see figure) has been fabricated successfully in the presence of surfactant F127. It is found that the building blocks of leaf-like PANI can be tuned from nanofibers (ca. 25 nm in diameter) to nanotubes (ca. 100 nm in diameter) with increasing monomer concentration. The proposed synthetic method will provide insight into the synthesis of oriented nanostructures of polymer materials by the soft-template strategy.