In the previous chapters, we described the behavior of the nematic-isotropic liquid and smectic B-smectic A interfaces in directional growth. Now we shall consider the instabilities that develop during the free growth of the interface between a columnar hexagonal phase and its isotropic liquid. In this type of experiment, the growth temperature is fixed, while in directional growth it is the velocity of the interface that is imposed, the sample being placed in a temperature gradient. These two techniques are therefore complementary.