Patanjali Yoga Sutra — नाभिचक्रे कायव्यूहज्ञानम् ॥3.30॥

nābhicakre kāyavyūhajñānam॥

Through saṁyama on navel or umbilicus (Nābhicakra), the yogi gets the knowledge of the anatomy and physiology of the body (Kāyavyūha).

Bhāvanopaniṣad praises this kāyavyūha and says, देहो नवरत्न द्वीपः॥2॥. Vyāsa Maharṣi says, नाभिचक्रे संयमं कृत्वा कायव्यूहं विजानीयात्॥. What is this kāyavyūha? It is the splendid assembly of:

The Electrical Engineering branch deals with electrical power and its application is found in all other branches of engineering. Similarly, kuṇḍalini yoga, a special branch of yoga deals exclusively with spiritual energy (called kuṇḍalini śakti), the awakening of different energy points (cakras), and stimulation of energy channels (nāḍis). Being the hub of different nāḍis reaching different parts of the body, Nābhicakra is also called as Maṇipura cakra, symbolised by ten petalled lotus. Yogi practicing saṁyama on this point gets knowledge of anatomy and physiology of the entire body.