Crow's feet are fine lines and wrinkles that radiate from the outer corners of the eyes, typically appearing in a fan-like pattern. They become more noticeable when you smile, squint, or make other facial expressions that engage the orbicularis oculi muscle around the eye. These lines are often among the first wrinkles to appear on the face because the skin around the eyes is thinner and more delicate than elsewhere, and it moves constantly throughout the day. Sun exposure, smoking, dehydration, and natural aging all contribute to their formation.