Soft tissue augmentation dates back more than 100 years, and over the past few decades, many agents and techniques have been introduced to cosmetically enhance soft tissue defects. With more patients now seeking aesthetic improvements without major surgery, the emphasis on soft tissue augmentation has received widespread acceptance among patients and physicians. With aging, reduced subcutaneous fat and dermal collagen results in soft tissue volume depletion, which may be superficial, as with facial rhytids, or involve deeper planes.

Collagen is the major insoluble fibrous protein in connective tissue and is the most abundant protein in the body. It provides the major structural component of the dermis, comprising 70% of dry skin mass. There are at least sixteen types of collagen, each denoted by a Roman numeral. Eighty to 90% of the collagen in the body consists of types I, II, and III. Type I collagen was the first to be isolated and characterized. Its fundamental structural unit is a long (300 nm), thin (1.5 nm diameter) protein that consists of three coiled subunits: two α1 chains and one α2 chain. Each chain contains 1,050 amino acids wound around one another in a characteristic right-handed triple helix. The collagen triple-helical structure contains an abundance of three amino acids, glycine, proline, and hydroxyproline, making up the characteristic repeating motif Gly-Pro-X, where X can be any amino acid.