Photographs from the 1862 book Mécanisme de la Physionomie Expression of interest pdf by Guillaume Duchenne. Through electric stimulation, he determined which muscles were responsible for different facial expressions.
Charles Darwin would later republish some of these photographs in his own work on the subject, which compared facial expressions in humans to those in animals. A facial expression is one or more motions or positions of the muscles beneath the skin of the face. Facial expressions are a form of nonverbal communication. They are a primary means of conveying social information between humans, but they also occur in most other mammals and some other animal species.
The pioneer F-M Facial Action Coding System 2. Freitas-Magalhães, and presents about 2,000 segments in 4K, using 3D technology and automatic and real-time recognition.