DNA replication is a complex process that involves numerous proteins. In addition, a group of 69- to 112-nucleotide-long, stem-loop, non-coding RNAs (known as Y RNAs) have an important role in this process: in mammals, they are essential for replication initiation in nuclei. But how does Y RNA result in the initiation of replication? On p. 2058, Torsten Krude and colleagues now shed light on the molecular mechanisms behind these events. During late G1 phase, Y RNAs specifically associate with unreplicated euchromatin, and the authors find that this selective binding is driven by the lower stem and loop domains of the Y RNA molecules. By contrast, in nuclei that have entered G2 phase, most Y RNAs are displaced from chromatin. Using pull-down and colocalisation assays, the authors go on to show that, at initiation sites, Y RNAs interact with proteins involved in initiating DNA replication – such as the subunits of the origin recognition complex (ORC), the chromatin licensing and DNA replication factors Cdt1 and Cdt6, and the DNA unwinding element binding protein (DUE-B). Proteins that belong to the DNA replication elongation machinery and to sites of replicated DNA, however, do not associate or colocalise with Y RNAs. Therefore, the authors conclude that, by binding to unreplicated chromatin, Y RNAs act as licensing factors that are required for replication initiation but do not have a role in chain elongation.