GHK-Cu is a naturally occurring copper complex formed by the tripeptide glycyl-L-histidyl-L-lysine (GHK) and a copper ion. It is naturally found in human plasma, saliva, and urine and has been studied for its regenerative, anti-inflammatory, antioxidant, and wound-healing properties. GHK-Cu is a popular ingredient in anti-aging and skincare products because natural levels of the peptide diminish with age.