It has been widely held that all that fathers essentially contribute to the next generation is half their genome. However, recent progress towards understanding biological processes such as sperm maturation and fertilization now indicates that the paternal contribution has been underestimated. To tackle some of the misconceptions surrounding the paternal contribution, the factors that are actually delivered by the sperm at fertilization and their potential developmental functions will be discussed using data from humans and animal models. Although still in their infancy, the practical applications of using sperm RNAs have already emerged in reproductive medicine as markers that are indicative of successful vasectomy. They are also beginning to appear in the forensic sciences and, within the next decade, might appear in the environmental sciences.