The structural scaffolding that surrounds cells in tissues — a complex mesh of proteins and sugars that gives tissues their architecture and mechanical properties.Major ECM components: collagen (tensile strength), elastin (elasticity), fibronectin and laminin (cell adhesion), hyaluronic acid (hydration and volume). ECM remodeling — breakdown and replacement of old matrix — is central to wound healing, follicle cycling, and tissue repair. GHK-Cu, matrixyl, and several injury recovery peptides target ECM remodeling via matrix metalloproteinase regulation and collagen synthesis stimulation. Excessive ECM breakdown impairs structure; insufficient turnover impairs healing.