FACS, or Facial Action Coding System, is a comprehensive and systematic method for measuring and describing facial expressions. Developed by psychologists Paul Ekman and Wallace Friesen, FACS breaks down facial movements into specific action units, allowing for a precise analysis of emotions and nonverbal communication. This powerful tool is widely used in fields such as psychology, anthropology, and even computer science to better understand human behavior and emotions. With its ability to capture the intricacies of facial expressions, FACS has become an invaluable resource for researchers and practitioners alike in unraveling the complexities of human communication.