Viral genome packaging and assembly are fundamental processes in virology, yet their mechanisms differ significantly between viruses. In double-stranded DNA (dsDNA) bacteriophages, a powerful molecular motor compacts the genome into the capsid under extreme pressures. In contrast, single-stranded RNA (ssRNA) viruses, the largest viral group on Earth, rely on spontaneous self-assembly without ATP-driven motors. Understanding the dynamics of ssRNA virus assembly has been challenging due to the fleeting nature of intermediates and the limitations of existing real-time observation techniques. In their study, Garmann et al. introduce an innovative single-particle imaging approach using interferometric scattering microscopy to monitor the assembly of the ssRNA bacteriophage MS2 with near-molecular accuracy. Their real-time data reveal a critical nucleation phase, indicating that assembly overcomes an initial free-energy barrier before proceeding via cooperative growth. The study highlights the influence of specific RNA-coat protein interactions, particularly packaging signals (PS), which guide and stabilize assembly. These findings challenge existing models and suggest that ssRNA viruses may adopt multiple assembly pathways depending on environmental conditions. The work by Garmann et al. opens new avenues for studying viral self-assembly with unprecedented temporal and spatial resolution, offering insights that could be applied to synthetic biology, antiviral strategies, and nanotechnology. Future research will aim to refine detection sensitivity and explore alternative RNA templates to further unravel the complexities of virus assembly.