Biofeedback trains people to consciously influence body functions that normally run on autopilot: brainwaves, muscle tension, skin conductance, heart rate, and pain perception. This episode of the In Search Of series looks at the instruments researchers use to make those hidden processes visible, translating electrical signals from the body into tones, lights, or readouts a person can watch and respond to in real time. The pitch is straightforward: once you can see a function, you can learn to change it, and with enough practice the change holds even after the sensors come off. The film treats biofeedback as a bridge between physiology and psychology, noting that as people gain control over measurable signals like muscle tone or skin response, shifts in mood, thought patterns, and behavior tend to follow. It stays close to the era's clinical claims about stress reduction and pain management rather than offering independent verification of them.