Yoga combines mental focus and physical exercise to help its practitioners achieve peace of both mind and body. Its stress- and anxiety-reducing properties are well-documented. In India, as well as in many other places in the world, yoga is studied using scientific methods and used to treat many mental and physical ailments. Yogic science seeks to authenticate cause and effect and develop principles based upon impartial observations. Yogic masters with credibility must have an extensive scientific education in the biological sciences and physics, among other disciplines.