This science or knowledge of healing, as mentioned in the Rig Veda, was revealed to Rishi Bharadvaja from the great Cosmic Intelligence. The knowledge consists of three aspects known as the Tri-Sutras of Ayurveda, which are - etiology or the science of the causes of disease, symptomatology or the study and interpretation of symptoms and medication and herbal remedies.

Approximately, during 4000-3000 BC, Sam Veda and Yajur Veda, the second and third Vedas came into being. Chanting of mantras and performance of rituals were, respectively, dealt in these two Vedas. And, during 3000-2000 BC Atharva the fourth Veda was authored, of which Ayurveda is an upaveda (subsection). Though it had been practiced all along, it was around this time that Ayurveda in India, was codified from the oral tradition to book form, as an independent science. It enlists eight branches/divisions of Ayurveda: Kayachikitsa (Internal Medicine), Shalakya Tantra (surgery and treatment of head and neck, Ophthalmology and Otolaryngology), Shalya Tantra (Surgery), Agada Tantra (Toxicology), Bhuta Vidya (Psychiatry), Kaumarabhritya (Pediatrics), Rasayana (science of rejuvenation or anti-aging), and Vajikarana (the science of fertility). The oldest treatise available on this codified version is Atreya Samhita.

Around 1500 BC Ayurveda was delineated into two distinct schools: Atreya—The School of Physicians, and Dhanvantari—The School of Surgeons. This made Ayurveda a more systematically classified medical science. Dhanvantari, who is considered to be a reincarnation of Lord Vishnu, was the guiding sage of Ayurveda. He made this science of health and longevity popular and widely acceptable. In fact, these two schools of thought led to the writing of two major books on Ayurveda—Charaka Samhita and Susruta Samhita.

These two Samhitas were written in the early part of 1000 BC. The great sage - physician Charaka authored Charaka Samhita revising and supplementing the text written by Atreya, which has remained the most referred Ayurvedic text on internal medicine till date. Susruta, following the Dhanvantari School of Thought, wrote Susruta Samhita, comprising the knowledge about prosthetic surgery to replace limbs, cosmetic surgery, caesarian operations and even brain surgery. He is famed for his innovation of cosmetic surgery on nose or rhinoplasty. Around 500 AD, Vagbhatt compiled the third major treatise on Ayurveda, Astanga Hridaya. It contained knowledge comprising the two schools of Ayurveda.

From 500 AD to 1900 AD, sixteen major Nighantus or supplementary texts on Ayurveda like Dhanvantari Bhavaprakasha, Raja and Shaligram among others were written incorporating new drugs, expansion in applications, discarding of old drugs and identification of substitutes. These texts mention about 1814 varieties of plants in vogue.

Evidences show that Ayurveda had nurtured almost all the medical systems of the world. The Egyptians learnt about Ayurveda long before the invasion of Alexander in the 4th century BC through their sea-trade with India. Greeks and Romans come to know about it after the famous invasion. The Unani form of medical tradition came out of this interaction. In the early part of the first millennium Ayurveda spread to the East through Buddhism and greatly influenced the Tibetan and Chinese system of medicine and herbology. Around 323 BC, Nagarjuna, the great monastic of Mahayana Buddhism and an authority on Ayurveda had written a review on Susruta Samhita. In 800 AD Ayurveda was translated into Arabic. The two Islamic physicians Avicenna and Razi Serapion, who helped form the European tradition of medicine, strictly followed Ayurveda. Even, Paracelsus, considered to be the father of the modern western medicine toed in line with Ayurveda.