Chandogya Upanishad is as old as Brhadaranyaka Upanishad and together they rank among the oldest Upanishads. Chandogya Upanishad was written on the Vedic Brahmana period about ninth to eighth century BC. Chandogya Upanishad is associated with Samveda. It is ranked ninth in the Muktika canon of hundred and eight Upanishadas.The Chandogya Upanishad depicts the importance and greatness of universal holy syllable 'OM' and the significance of vital life force or 'Prana'. It also narrates a story to explain the holiness of Prana narrating how the evil forces could not touch it while the other five senses got defiled by the evil.
