Each of the Vedas has several Brahmanas and Aranyakas. There are two Brahmanas for Rig-Veda, Aithareya and Sankayana. The Sathappatha Brahmana belongs to Sukla Yajur-Veda. Krishna Yajur-Veda has Thaithreya and Maithrayana Brahmanas. The Thandaya or Panchavimsa, Chhandogya, Adbhutha, Arsheya and Upanishad Brahmanas belong to Sama-Veda. Atharva-Veda has Gopatha Brahmana. They list all the Vedic Karmas or Rituals to be performed and explains how they are to be performed. Each of them has an Aranyaka which explains the inner meaning, the doctrine and philosophy contained in the Samhithas as manthra and in the Brahmanas as Karma. They enlighten us about the Vedas, to understand why Yajnas and Rituals are required to be done. The Upanishads, as the concluding portion of the Vedas, give us the essence of the Philosophy. There were 1081 Upanishads one for each Sakhas of the Vedas. Of all these sections Upanishads, many of the Sakhas are lost but we have some Upanishads though the related Mantra-Samhita is not available.

The most important Upanishads are: Isa, Kena, Mundaka, Mandukya, Thaithriya, Katha, Chhandogya, Brihadharanyaka, Aitreya, Prasna, Kaushithaki, Svethasvathara and Maithrayani. We also have Maha-Narayana and Bashkala Manthropanishad. Many modern researchers have done laudable works of collecting fragments of more than 16 more Brahmanas and 188 Upanishads. The Four Upa-Vedas are Ayurveda, Dhanur Veda, Gandharva Veda and Arthasasthra. There are Six Vedangas; of which are Siksha and Vyakarna by Panini; Chandas by Pingalacharya and Niruktha by Yaska were explained in an earlier chapter. These four books deal with the language of Vedas and its correct usage and pronunciation. Jyothisha by Garga is a study of Astronomy and Astrology dealing with planetary movements and calculations and their influence on human life and activities. Kalpa is the method of rituals. Of this, we have Srautha, Grihya, Dharma and Sulba belonging to the authorship of various Rishis.

" All this cosmic universe is the eternal word Om. Its further explanation is this: the past, the present, the future and everything is just Om. - And whatever transcends the three divisions of time -- that too is just Om. -.. Thus the Word Om is verily the Self [Ãthman]. He who knows this, with his self [Jiva], enters the Self [Ãthman].

-- [ Maandukya Upanishad ]