Glycine

Glycine is a small-molecule nonessential amino acid. It's a proteinogenic amino acid, an important precursor of collagen which contains about 35% glycine in the chain. In short, it's one of the most important beads in a chain providing firmness to our skin.

Also, glycine is one of the essential NMFs (natural moisturizing factors) enhancing skin's moisture-binding ability and protecting from dehydration.