The Immortal Germline, Volume 135 in the Current Topics in Developmental Biology series, highlights new advances in the field, with this new volume presenting interesting chapters on a variety of topics, including Balbiani body, germ plasm and polarity, Wolbachia and the germline, Human germ line biology, Reproduction/immunity and sperm success, Mammalian spermatogenesis, Reproduction/regeneration and germ cells in planarians, Germline stem cell homeostasis, Germline soma interactions/sex determination, Reconstituting the mouse germ-cell specification pathway in vitro, Maternal Germ line inheritance of mitochondria, Transposon strategies, and more.