To overcome these limitations, we performed differential scanning calorimetry measurements and fluorescence experiments of binary and ternary lipid mixtures corresponding to the L o phase, and provided a molecular picture of the observed phenomena with atomistic molecular dynamics simulations. We studied bilayers consisting of 1) a ternary mixture consisting of 55 mol% DPPC, 15 mol% DOPC, and 30 mol% CHOL, corresponding to the composition of the L o phase of a phase-separated 0.40/0.40/0.20 mixture at 298 K. Upon heating, this mixture remains in the L o phase. 2) A binary mixture of 70 mol% DPPC and 30 mol% CHOL, which falls to the L o regime at all relevant temperatures. The simulations revealed distinct changes in bilayer structure depending on the temperature, as shown in Fig. (see Figs. S1 and S2 for more temperatures). At 293 K, DPPC chains are arranged in all-anti conformation, whereas at 333 K they are predominantly in gauche conformation in both binary and ternary mixtures. At 313 K, their behaviors differ with the former showing more ordered chain conformations. This indicates that DPPC undergoes some kind of a transition yet at different temperatures for the two mixtures. The question is whether this transition is visible in membrane properties.