The formation of cubic phases was tested through the self-assembly of MO molecules in water at the experimental excess water point (40% weight water). The formation of a unit cell of the expected 𝑄 𝐼𝐼 𝐷 mesophase was confirmed through a surface fit of the ideal surface 171, 172 to the terminal tail bead of the system (Figure ). The stability of the cubic phase was further confirmed by self-assembly simulations at multiple temperatures and compositions (Figure ). While cubic phase self-assembly was achieved in both Martini 2 and Martini 3 force fields, the unit cell sizes in Martini 3 were in general slightly smaller at similar compositions. Further, the phase transition from cubic to hexagonal at high temperatures was confirmed through temperature annealing simulations (Figure ,F). The 𝑄 𝐼𝐼 𝐷 -𝐻 𝐼𝐼 the transition was observed at around 347±4 K, slightly lower than the experimental transition at around 363 K, which again could be complicated by metastability. One challenge we faced was the simulation of multiple cubic unit cells. While multiple unit cell simulations have been performed