Although yoga is generally, and mistakenly, thought to be physical postures, that is only a small part of yoga. Yoga is a spiritual science by which one seeks to know oneself on all levels, physical, mental, spiritual and to attain self-mastery. Meditation is the heart of yoga and most of yoga is composed of psychology, philosophy, lifestyle, and practice-- which is aimed at achieving deeper awareness. The physical exercises are just a small part of yoga and are not essential to its practice. One practices yoga to know directly the ultimate Truth of life, In the process, one may also derive the most from this gift of life, and be of service to others.