In the present work, a simple and effective approach has been employed to fabricate the polystyrene/polyaniline (PS/PANI) composite microspheres with various morphologies. PS/PANI composite microspheres exhibiting different structures such as sea-urchin like, core-shell structure, have been synthesized by seeded emulsion polymerization with polystyrene microspheres as seeds. In particular, the sea urchin-like PS/PANI composite microspheres, with radial array nanofibers on the surface, have demonstrated the switchable wettability between superhydrophilicity (0 degrees) and superhydrophobicity (152 degrees) under the response of either electrical potential or pH. This intelligible approach can produce sea urchin-like PS/PANI composite microspheres in bulk. The growth mechanism of sea urchin-like PS/PANI composite microspheres has also been elucidated. Following the dissolution of the PS template, the sea urchin-like polyaniline (PANI) hollow microspheres are obtained. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.