Skin is a multifunctional organ but, alongside every other organ system, is subject to both intrinsic and extrinsic aging. Whilst both ageing processes are associated with phenotypic changes in cutaneous cells, the major functional manifestations of ageing occur as a consequence of structural and compositional remodeling of normally long-lived dermal extracellular matrix proteins, flattened dermal-epidermal junction (DEJ), and weaker epidermal function. Many researchers revealed that dermal fibroblast which mainly synthesis the collagen and elastin in dermis, while the epidermal keratinocyte and DEJ are lesser described, especially for peptides. A new palmitoyl oligopeptide complex PTC, which consists of hydrolyzed collagen and oligopeptide, was identified in both keratinocyte and fibroblast, and finally verified in human skin. All data suggest PTC had a 3D theory against skin aging: from epidermal keratinocyte to dermal fibroblast, especially containing the structural proteins of DEJ.