The volume percentage of the hydrophilic inner and hydrophobic outer phases was estimated using the 3D images of three separate BBOA particles at an RH of 58 ± 2 RH % (e.g. in Fig. ) to be 51 ± 5 % hydrophilic phase and 49 ± 5 % hydrophobic phase, for the 400 °C smoldering temperature. This ratio may be dependent upon the combustion conditions, as the chemical composition of BBOA has been shown to be dependent upon variables such as the fuel type, whether smoldering or flaming combustion occurred , and the combustion temperature, which can range from roughly 200 °C to > 700 °C . In this work we have resolved two phases in particles down to a size of ~ 6 µm, resulting from LLPS (Fig. ). Previous work suggests that LLPS may be suppressed at particle diameters < 40 nm due to finite size effects and hence, we expect the core-shell morphology to exist for BBOA particles larger than 40 nm, although further experiments are required to confirm this.