Soft tissue fillers, or "fillers" in short, are products which are intended to fill up defects in the soft tissues, typically wrinkles, folds and dents in the face. Some fillers are intended to add volume, for example to the cheekbone or the chin and are often used for lip enhancement. There are many products on the market. The most important distinction is between non-permanent fillers, which disappear spontaneously after a while, and the permanent fillers, which stay embedded in the tissues forever. Most non-permanent fillers are quite safe to use, but here also it is advisable to demand fillers that are generally accepted, or FDA approved, such the ones based on hyaluronic acid, collagen and calcium hydroxylapatite microspheres. Fillers are injected directly into the area to be treated, often after application of a topical anaesthetic cream. The effect is immediate, and lasts between 2-18 months, depending on the type of product and the treated area. Always demand to know which product your physician is going to use.