Raj Yoga has been divided into two groups of four limbs each. Out of these, the first four stages (Yama, Niyama, Asana and Pranayama) are known as the external or bahiranga yoga as they change the external personality behaviour and action which are related to the interactions in the world. The last four stages (Pratyahara, Dharana, Dhyana and Samadhi) constitute the antaranga yoga, the inner yoga which works with the mind and makes one experience the full mind from the initial state of sensory withdrawal to the state of Samadhi, which is unity of all the faculties of the mind. It is a mental process of observation, analysis, reflection, comtemplation, meditation and achievement. These last four stages stop the input of further impressions or vrittis into the field of consciousness.