Wrinkle is synonymous with the process of aging. Our skin consists of three layers- epidermis, dermis and subcutaneous fat layer. As we age the cells of the epidermal layer becomes thin and less sticky. This loss of stickiness causes the moisture present under the epidermis to get released from the upper layer, causing dryness of the skin.
In the subcutaneous layer, the size of fatty cells decreases with age and it fails to provide enough support to the upper layers and if ths occurs sagging is quite noticeable.