What is the difference between a wrinkle and a fine line? A wrinkle is defined as a crease or furrow in the skin caused by the natural process of aging, by excessive exposure to the sun's damaging rays, or environmental insults. For example, if you look in the mirror and see crow's-feet around your eyes — these are wrinkles. If you stretch a wrinkle in the crow's-feet area, you will still see it.

However, a fine line (or "expression line") is a small wrinkle that may be caused by the contraction of facial muscles during smiling or frowning. When you stretch the skin of a fine line, the lines are barely visible. When these muscles contract, they pull the skin in, causing a line. And the muscles controlling frown lines between the brows may contract even when the muscle is resting, causing deep lines — which could result in the start of a wrinkle.