This review article examines the current state of knowledge regarding skin permeation of GHK-Cu (a copper tripeptide used in antiaging products) when formulated in liposomal delivery systems, evaluating whether adequate measurement methods exist to assess this property (review-level evidence). The authors assess existing permeation testing methodologies and their applicability to this specific encapsulated formulation. The review identifies gaps in standardized measurement approaches for evaluating how effectively liposome-encapsulated GHK-Cu penetrates skin layers.