Healthy young skin contains collagen that gives it volume, flexibility, and strength.As one ages, natural collagen begins to break down and volume is lost. Skin becomes damaged and thins and loses elasticity. Fat tissue is lost. These losses of volume and elasticity results in fine lines, wrinkles, and skin laxity which is perceived as a loss of our youthful appearance.
An appropriate filler can eliminate shadows, hollows, and concavity on the face and restore the soft contours characteristic of younger skin, and provide a path for your face to return to a more youthful shape.
Soft tissue fillers are made from substances that can be injected into the skin to counteract the appearance of aging and help reduce fine lines and wrinkles.They can also be used to give more volume to lips, fill a hollow in the cheeks,improve scars and facial imperfections, and help to elevate deep facial folds.The result is a more youthful appearance which does not involve surgery orcutting of the skin, thus minimizing risk.
A variety of fillers is now available to help achieve this goal of apparent skin rejuvenation:
Hyaluronic acid products are nearly identical to the hyaluronic acid naturally found in the body. It naturally occurs in the skin, cartilage, joints and the eye. In skin tissue, hyaluronic acid fills the space between collagen and elastin fibres. The role of hyaluronic acid in skin is to deliver nutrients, hydrate the skin by holding in water, and to act as a cushioning agent. Unlike use of bovine collagen, there is no need for pre-testing.
Calcium hydroxyapatite filler (market name: Radiesse) is another kind of fillers that replenishes volume and stimulates the production of your own collagen. 
Polycaprolactone is another biodegradable material which can be used as a filler. This material is the basis of the ELLANSE filler.