The differential scanning calorimetry thermograms of suspensions of trimyristin nanoparticles in the stable P-polymorph display several melting events. Particle thickness distributions obtained by analysis of difference X-ray diffraction patterns recorded during melting reveal that these discrete events correspond to the melting of classes of particles differing in thickness by only one unit cell. A large increase in lattice constants with decreasing particle thickness was observed, indicating that classical surface thermodynamics is not applicable to particles consisting of only a few molecular layers.