Wat does collagen do? Collagen is one of the most important building blocks for our joints, bones, muscles, hair, nails, connective tissue and skin. Collagen provides elasticity and strength to all our connective tissues, including skin, tendons, joints, cartilage and bones. Collagen is a glue-forming protein; it holds everything in our body together, makes it supple and gives it strength. In the skin, too, collagen provides firmness and elasticity. When we age and the collagen production decreases, the firmness of the skin decreases, which results in wrinkles. Curious what else collagen does for the skin? Read this article!