Yamas are social moral conduct. Niyamas are to be observed for self-development. Asana is a comfortable, steady and peaceful posture to make the physical body strong and ready for inward journey. Pranayama is the controlling of bio-energy. The first four steps are external aid called Bahiranga and last three are internal aid called Antaranga.. Pratyahara is the link between external and internal. It consists of controlling of five sense organs. In the Sadhana pada chapter, patanjali explains the journey from yama to pratyahara.