Chandogya Upanishad

छान्दोग्योपनिषद्

One of the oldest and largest Upanishads, in eight chapters (prapathakas). Contains the celebrated dialogue between Uddalaka Aruni and Shvetaketu — teaching Tat Tvam Asi (That Thou Art). Also covers the Udgitha (OM chanting), Prana as Brahman, the story of Satyakama, and the city of Brahman in the heart.