The observations presented here are at a MO concentration of 1.4 mg/ml, which results in a MO/DOPC molar ratio of ~250. However, this is not the molar ratio of MO/DOPC in the mixed GUV membranes. The average swelling ratio of GUVs with an average diameter of 11 ± 4 µm was found to be 19 ± 11% within 20 min of LCNP incubation (Table ). Taking the molecular surface area of DOPC to be 0.72 nm 2 , and the polar molecular surface area of MO to be 0.33 nm 2 , we estimate the average molar ratio of MO in the GUV membrane to be 45 ± 17 mol%. Comparing our calculation to the phase diagram of MO/DOPC, where equilibrium mixtures are found to be in the lamellar Lα phase up to ~75 mol% MO, we predict that these mixed systems are still in the lamellar phase of the equilibrium phase diagram within the studied time scale. At this ~45 mol% MO composition, the membranes dynamically undergo morphological transitions that re-equilibrate the GUVs by decreasing the excess membrane area until they return to their near-spherical final state. Note that fission and fusion events during the studied time scale will decrease or increase the swelling ratio, which might affect the calculated number of LCNPs incorporated per GUV.