After having studied nematic anchoring on solid substrates, we shall now study the interface between the nematic phase and its melted isotropic liquid. Because the material is the same on both sides of the interface, the two phases can be described by the same order parameter, the quadrupolar moment Sij. This parameter describes symmetry breaking at the transition. Unlike density or impurity concentration, it is not conserved; its equilibrium profile across the interface will therefore be easily determined. Nevertheless, complications appear when submitting the interface to chemical or mechanical constraints, as it can deform or become unstable. In addition to the well-known MullinsSekerka instability, developing when the nematic phase grows into its isotropic liquid, instabilities of elastic origin can appear when the nematic is confined to a restricted volume.