Crystallization on superhydrophobic surfaces. (a) Graphical view of crystallization in a container, showing nucleation sites both in solution and along the sides of an uncoated glass test tube for CuSO4 crystals. (b) Crystal growth in a container coated with superhydrophobic paint, indicating the surfaces' nano-roughness. Nucleation was observed only in solution but not along the container walls. (c) SEM image of the superhydrophobic coat on a glass test tube, showing the nano-rough surface structure.