Here you have an introduction to faces and what kind of stimuli they are, what kind of responses they elicit, and to the facial expressions of emotions (mobility, variety, adaptive value, non-verbal communication). Also the interaction between gaze and social attention and its integration with other facial cues is described. Finally, some data of facial and social signal processing is presented: third person perspective on social perception, the role of the amygdala, the liking effect induced by gaze, etc.