Biofeedback utilizes a system of sensitive instruments that relay information about the physical condition of the body. Used as a primary therapy, or in conjunction with other methods, biofeedback provides deep relaxation and stress management skills to prevent stress-related disorders and illness. These skills, including deep breathing and guided imagery, offer self-regulation and control over mental, emotional, and physical processes. The principles of biofeedback can be traced back to the 18th century.