The most popular fillers in the world are made of hyaluronic acid, which is a naturally occurring substance in the body that helps to hydrate and plump the skin.
Have you used a high-end gel-based facial serum before? If so, that's probably made of hyaluronic acid. It draws in your natural youthfulness to restore lost facial volume.
In filler form, the hyaluronic acid chains are cross-linked to form a thicker, responsive gel. Once injected into specific areas of the face, it feels and acts just like your own body.