Facial expression lines develop from the movement of the underlying muscles on the overlying skin. Although these lines help us to convey to others a range of emotional states, some facial expression lines always seem to connote fatigue or anger, even if those appearances do not represent how we are feeling. This is especially true of lines of the forehead and between the eyebrows. Other lines, such as crow’s feet, may make us appear older than our chronological age. By the time we are in our 3 rd or 4 th decade and sometimes younger, permanent creases and furrows, known as Wrinkle lines, develop in the skin along these facial expression lines.