What causes lines and wrinkles?

Movement of your faces’ muscles causes the skin to crease.

As skin becomes less elastic over time, repeated frowning may create visible lines and wrinkles. Frown lines (those between the eyebrows) and crow's feet (lines that radiate from the corners of the eyes) appear to develop because of permanent small muscle contractions. Habitual facial expressions also form characteristic lines.

As a person ages, skin undergoes significant changes: The cells divide more slowly, and the inner layer of skin becomes thinner.

Fat cells beneath the skin begin to diminish and the underlying network of elastin and collagen fibres, which provides scaffolding for the surface layers, loosens and unravels. The skin loses its elasticity. When pressed, it no longer springs back to its initial position but instead sags and forms furrows. Gravity exacerbates the situation, contributing to the formation of jowls and drooping eyelids. (Eyebrows, surprisingly, move up as a person ages, possibly because of forehead wrinkles.)