Finally, we have investigated whether the crystallization of C30d inside DMPC is affected by the low amount of water in our systems. Figure shows DSC heating and cooling runs of 5 vol% C30d in DMPC in excess water conditions. There are two important differences compared to the reduced hydration sample: First, the DMPC main transition is not at all affected by the presence of C30d. Second, the cooling transitions of C30d are shifted to much lower temperatures: the liquid-to-rotator and rotator-to-crystal transition occur at 19.5 and 20.5 • C below the bulk C30d melting temperatures, respectively. Such a strong hysteresis between heating and cooling transitions is evidence for homogeneous nucleation of C30d . We previously showed that under excess water conditions, n-alkanes induce the formation of smaller lipid structures (vesicles or maybe micelles with alkane droplets) . Confinement in such small structures could explain why homogeneous nucleation is possible in this system. Furthermore, the unaffected lipid transition supports this interpretation, since the alkane would be spatially separated from most of the lipid in this scenario.