Peptides are small molecules that can penetrate the barrier of the epidermis and have an impact on the dermis, or deeper layer of skin. These have the advantage of producing rapid, visible changes in the appearance of the skin. Specifically, they can cause tightening and the appearance of firming in the skin. Algae peptides are a unique extract from the Hawaiian Sea that have a component called hydroxyproline, an unusual amino acid that is rarely found in the skin except within its own collagen.  Algae peptides are particularly impressive in their moisturizing and firming properties when applied to the skin. 
Peptides are the chemical name for a chain of amino acids – and cosmetic chemists differentiate between the peptides that are not proven beneficial to the skin and peptides that are. When a peptide has proven in laboratory testing to have beneficial effects on the skin, it is classified as an active peptide. The family of active peptides is wide ranging – and when applied topically to the skin they can produce dramatic results. In one study of peptides, more than 30% of the people who used them saw an immediate improvement in their skin, while an additional 5% saw improvement after several hours. Almost 70% of users reported tightening and firming within two weeks.