The Chandogya Upanishad, one of the oldest and most prominent Upanishads embedded within the Sama Veda, focuses on meditation, sacred sound, and the ultimate nature of reality. It emphasizes meditating on the sacred syllable Om as the essence of life, breath, and cosmic harmony. Through the famous dialogue between Sage Uddalaka and his son Svetaketu, it teaches Tat Tvam Asi ("That Thou Art")—the truth that the individual soul (Atman) is identical to the universal divine reality (Brahman). It reveals that the vast universe exists within the small space of the human heart, encouraging inner self-realization over external rituals.