Full description and mechanics of the code can be found in reference . Briefly, the tomogram slices were first Canny filtered using FIJI. The apparent bilayer thickness is defined as the minimum distance between pixels on the inner and outer leaflet. Bilayer measurements from 20-30 images of each pure system were used to determine which observed distances in the hybrid compositions were categorised into polymer-like or lipid-like phases. The domains were mapped on to the individual tomograms of each hybrid vesicle composition by calculating the probability of each observed distance corresponding to either the polymer-like or lipid-like phase.