This research provided quantitative evidence on the microstructural transformation due to the phase separation in epoxy-modified bitumen in the domain of epoxy contents from 10 to 90 % by confocal fluorescence microscopy (with the effective pixel size of 21.5 μm) as the systems approached their ultimate state of hardening. The image analysis of phases representing bitumen and epoxy included particle size distributions and spatial arrangement (of discrete droplets) and the local thickness distributions (of percolated structures). The results showed that these systems underwent substantial transformed from a solution of epoxy droplets in bitumen to a quasi-bimodal dispersion of bitumen within an epoxy networked structure, with the catastrophic phase inversion taking place between 40 and 50 % of epoxy. The morphology of phases and their spatial arrangement confirmed that mechanical interactions determined the packing of hyperdispersed droplets (as the systems approached the phase inversion), while the relaxation of surface tensions weakened the interlocking and eased the movability of droplets (far away from the inversion point). This contributed to understand how the microstructure directly resulted from the interfacial tensions between phases. Transformation in the phase inversion zone and the interfacial diffusion, including spectroscopic techniques, were recognised as particularly relevant for further research.