In order to understand the origin and mechanism of the pronounced magnetodielectric coupling in NiTiO3, researchers from Heidelbergs Kirchoff Institute of Physics grew large, high-quality single crystals of this compound by means of the optical floating-zone technique (ScIDre HKZ two-mirror vertical configuration optical furnace and a four-mirror horizontal configuration) under various atmospheres and at different pressure. The single crystals were used for high-resolution studies of thermal expansion and magnetostriction along the crystallographic a and c axes, respectively. From thermal expansion and magnetostriction studies an anisotropic magnetic phase diagram was constructed.