The semiconductor-metal phase change in VO2 at approximately 67 degrees C, which results in great changes in its optical, electrical, and magnetic properties, is described in detail. The synthesis of VO2 thin films by the sol-gel method is outlined and the structure and optical properties are characterized, including hysteresis phenomena in the transmittance-temperature and reflectivity-temperature plots. A mechanism of the phase change-confirmed to be the monoclinic-to-tetragonal rutile transition-is proposed based on coordinative field theory.