Yoga Nidra 
Yoga Nidra is a methodical relaxation process which induces true relaxation while maintaining consciousness. In normal sleep, consciousness is absent and the unconscious is in charge. In Yoga Nidra the consciousness directs the unconscious to relax. This achieves complete relaxation and releases unwanted patterns from the unconscious. These unwanted patterns (samskaras) are not completely released in normal sleep and can cause illness and dysfunction in conscious life. Yoga Nidra has been developed from the Ancient Tantras.