The scope of the book is to explain the mechanism of augmenting or suppressing the onset of thermomagnetic convection in ferrfluids with or without porous medium in the presence of uniform vertical magnetic field under the influence of magnetic field dependent (MFD) viscosity, internal heat source strength, temperature dependent viscosity, surface tension forces, cubic temperature profiles, vertical throughflow and an external constraint of rotation for various types of velocity, temperature and magnetic boundary conditions. The different problems explained in the book find an applications in many fields of science and engineering problems of practical importance.