Bellafill is collagen filler injected under the skin to plump and smooth imperfections such as wrinkles, smile lines and acne scars. It is composed of collagen as well as PMMA microspheres. Collagen is a protein found in the skin that provides an elastic and youthful appearance. Injections of collagen produce immediate results but these results diminish over time when the body breaks down the collagen. PMMA microspheres are tiny beads that serve as a scaffolding for the collagen that your body naturally creates.