Peptides aimed at skin, hair, and visible ageing. GHK-Cu (a copper peptide) actually has some human topical-skin data and is widely used in serums; that is the exception. Most cosmetic peptide claims, and certainly anything injectable in this category, rest on cell-culture studies and marketing. Melanotan II, for example, has real safety concerns including mole and melanoma risk. Topical and injectable are very different conversations.
Cluster assignment reflects each peptide’s primary intent, its main reason for being on the site. Some peptides span clusters in practice (tesamorelin is approved for HIV-associated visceral fat but is also chased by bodybuilders); we file each under one canonical cluster and link out where the cross-over matters.