Membranous organelles allow subcompartmentalization of biological processes. However, additional subcellular structures create dynamic reaction spaces without the need for membranes. Such membraneless organelles (MLOs) are physiologically relevant and impact development, gene expression regulation, and cellular stress responses. The phenomenon resulting in the formation of MLOs is called liquidliquid phase separation (LLPS), and is primarily governed by the interactions of multidomain proteins or proteins harboring intrinsically disordered regions as well as RNAbinding domains. Although the presence of RNAs affects the formation and dissolution of MLOs, it remains unclear how the properties of RNAs exactly contribute to these effects. Here, the authors review this emerging field, and explore how particular RNA properties can affect LLPS and the behavior of MLOs. It is suggested that posttranscriptional RNA modification systems could be contributors for dynamically modulating the assembly and dissolution of MLOs.