In this paper, we report the obtention of In2O3 nanostructured microwires by the decomposition thermal treatment of InSe single crystal in two-steps under an oxygen-ammonia flow without the presence of any catalyst. Long In2O3 microwires with uniform shape and homogeneous surface were first synthesized through thermal treatment of InSe single crystal at temperature of about 640 degrees C; then, furnace temperature was increased to 750 degrees C and, as annealing time proceeded, the obtained microwires served as substrates on which nanorod branches grew. The shape and the structure of the microarchitectures were characterized by means scanning electron microscopy, transmission electron microscopy, selected area diffraction pattern, X-Ray diffraction and Raman spectroscopy. Our results indicated that In2O3 primary wires with a clean surface grew in the [100] direction and that the secondary protuberances grew in the [011] direction. A possible growth mechanism of the hierarchical microwires was also proposed. (C) 2012 Elsevier B.V. All rights reserved.