Replication and genome encapsidation of many negative-sense RNA viruses take place in virus-induced membraneless organelles termed viral factories (VFs). Although liquid properties of VFs are believed to control the transition from genome replication to nucleocapsid (NC) assembly, VF maturation and interactions with the cellular environment remain elusive. Here, we apply in situ cryo-correlative light and electron tomography to follow NC assembly and changes in VF morphology and their …