Yin yoga is based on the Taoist concept of yin and yang, opposite and complementary principles in nature. Yin is the stable, unmoving, hidden aspect of things; yang is the changing, moving, revealing aspect. In the body, the relatively stiff connective tissues (tendons, ligaments, fascia) are yin, while the more mobile and pliable muscles and blood are yang. A Yin yoga class usually consists of a series of long-held, passive floor poses that mainly work the lower part of the body - the hips, pelvis, inner thighs, lower spine