 mammalian sperm are carriers of not only the paternal genome but also the paternal epigenome in the forms of DNA methylation, retained histones and non-coding RNAs. Two myrna clusters consisting of five myrnas, mere 34bc are present in sperm but absent in ocytes. Injecting sperm into wild type ocytes led to normal fertilization, normal pre-implantation development and normal birth rate. This article was authored by Shu-H.R. Yuan, Chong-Tang, Ying-Zhong and others.