Remote photoplethysmography—rPPG for short—is a camera-only way of reading pulse-related colour changes in your face. Each heartbeat shifts the balance of red and green light reflected by skin; a neural network tracks those micro-changes frame-by-frame, cancels motion and lighting swings, and rebuilds the same photoplethysmogram waveform you’d get from a fingertip sensor. From that waveform it derives heart-rate, breathing rate and other vitals in real time. Learn more in our rPPG explainer article .