Most dermatologists understand fine lines as being one to two millimetres in depth. The folds are shallow, caused by sagging and dry skin.
Wrinkles, on the other hand, are deeper than 2mm. They are predominantly caused by muscle contractions, like frowning and smiling, during facial expressions. Repeated facial muscle movements create folds over the years.
There are different types of wrinkles to understand too:
Occurs only with facial movements such as frowns or squints.
Fine lines occur in the earliest signs of ageing. Collagen breakdown and repeated muscle movements cause wrinkles.