Mitochondrial diseases have a peculiar character of variability that expands from DNA, cell and tissue/organ levels to family/society level. These kinds of variability seem an obstacle to prevent us from developing new and effective therapies for this disease. Selective delivery system to mitochondria can make us get a promising new strategy to treat and prevent the disease. MITO-Porter may be a powerful system in which we can introduce a various kind of materials including DNA, RNA, enzyme and drugs to mitochondria in vivo.