Our skin has two layers: the epidermis (outer lump) and the dermis (out cold the epidermis). Wrinkles happen in the dermis. The dermis is made happening of collagen and added proteins. As we age, our bodies fabricate less collagen. The collagen is what makes our skin elastic and mild. Less collagen results in saggy skin taking into account wrinkles. Lots of factors contribute to this process. Here are some:

Sun broken
Smoking
Dehydration
Poor nutrition
Facial expressions (laughing, squinting, etc.)
Pollution and toxins
Natural aging
Sleeping upon your side ( gone your cheek pushed nearby your pillow)