Molecular dynamics simulation of a united-atom model of the lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) at the temperature 298 K, pressure 1 bar, and hydration level 57 water molecules per lipid. The results are shown as a rendering of the final configuration overlain with a 50 ns trajectory of a single water hydrogen sampled at 10 ps intervals (black lines). The lipids are assembled into ∼5 nm thick bilayers with the hydrophilic headgroups (red) separating the hydrophobic tails (yellow) from the water (blue). The brightly colored region (left) comprises four replicas of the rectangular simulation box with 128 lipid molecules. The zoom-in (bottom right) shows a 10 ps segment of the hydrogen trajectory at the full 2 fs time resolution of the simulation (black dots) and the final location of the water molecule (blue). (GROMACS23 simulation results redrawn from ref. 25 using the POV-Ray freeware60 ).