Humanin (HN) is a short peptide, as shown in Figure 1, consisting of 21 or 24 amino acids (depending on mitochondrial or cytoplasmic translation, respectively), and it was discovered in 2001 by Nishimoto Lab [17,18] during a screening of neurotrophic factors that inhibited apoptosis induced by a pathological amyloid beta mutant in Alzheimer’s disease [19]. The gene discussed is MT-RNR2; the disease is Alzheimer disease.