SS-31 (Elamipretide) is a novel, cell-permeable tetrapeptide (D-Arg-Dmt-Lys-Phe-NH₂) specifically designed to target and protect mitochondria. With its unique alternating aromatic-cationic structure, SS-31 selectively accumulates in the inner mitochondrial membrane, where it interacts with cardiolipin to stabilize mitochondrial structure, reduce oxidative damage, and improve cellular bioenergetics. This research peptide represents a breakthrough tool for investigating mitochondrial dysfunction, age-related cellular decline, and diseases characterized by impaired energy metabolism.