The face is a con­stant flow of facial expres­sions. We react and emote to exter­nal stim­uli all the time. And it is exact­ly this flow of expres­sions that is the observ­able win­dow to our inner self. Our emo­tions, our inten­tions, atti­tudes, moods. Why is this impor­tant? Because we can use it in a very wide vari­ety of appli­ca­tions.