In 2S 3 has a defective spinel structure. The indium ions in tetrahedral interstices disorder at 420° C whereas the indium ions in octahedral interstices disorder at 780° C. The order-disorder process is observed in the electron microscope and different types of interfaces resulting from the ordering of indium ions (or indium vacancies) are studied. It was possible to identify twins and anti-phase boundaries due to the ordering of tetrahedral indium ions and anti-phase boundaries resulting from the ordering of octahedral indium ions.