Yin Yoga is based on Chinese Meridian Theory of healing practice. According to this theory, energy in the body runs through energy pathways -called the meridian system/pathways through out the body through the connective tissues. Connective tissues are everywhere in the body, it is in the dermis of the skin, it forms and interpenetrates every bone, every joint, every organ, tissue, and cell. Hence, connective tissue is a vital meridian tissue which conducts life giving energy to all the cells and organs of the body.
In Yin yoga, the postures are held for 3 to 5 minutes. This allows for gentle stretch, energy flow, and rehabilitation of the connective tissues.