This book presents research studies on equilibrium statistical behaviour of liquid crystals, where the nematogenic molecules are modeled such that they have either uniaxial or biaxial structure. Biaxial nematic phase, although predicted theoretically more than four decades ago, has only recently been verified experimentally in thermotropic liquid crystals. Presence of electric dipole moment in a mesogenic molecule could stabilize the biaxial phase and this has been described in this volume. Nematic-Isotropic phase transitions in an external magnetic field show important properties depending upon the uniaxial or biaxial characters of the molecules. This book includes all these interesting features.