  Facial expressions are an ideal means of communicating one's emotions or
intentions to others. This overview will focus on human facial expression
recognition as well as robotic facial expression generation. In case of human
facial expression recognition, both facial expression recognition on predefined
datasets as well as in real time will be covered. For robotic facial expression
generation, hand coded and automated methods i.e., facial expressions of a
robot are generated by moving the features (eyes, mouth) of the robot by hand
coding or automatically using machine learning techniques, will also be
covered. There are already plenty of studies that achieve high accuracy for
emotion expression recognition on predefined datasets, but the accuracy for
facial expression recognition in real time is comparatively lower. In case of
expression generation in robots, while most of the robots are capable of making
basic facial expressions, there are not many studies that enable robots to do
so automatically.
