A wurtzite-structured CdSe nanosaw (see Figure) is formed by a two-step process: a fast-growth process along [0110] creates the main ribbon, while a subsequent side-growth process along [0001] creates the one-sided teeth. The growth of the teeth is suggested to be a combined result of secondary epitaxial nucleation processes resulting front a zinc-blende-wurtzite phase transformation and the self-catalytic effect of the Cd-terminated (0001) surface.