Superimposed external magnetic fields during electrodeposition process offers the possibility to tailor microstructure and properties of the obtained films in a very efficient, contactless, and easily controllable way, what is caused by so-called magnetohydrodynamic MHD effect. On the other hand, the nonequilibrium state of aselectrodeposited nanocrystalline films provides a strong thermodynamic potential for microstructural transformation. This means that the benefit effect of magneto-electrodeposition on a nanocrystalline film can be completely consumed by a thermal exposure at relatively low temperature. Magnetic field annealing has been confirmed to be useful for tailoring the microstructure of as-deposited nanocrystalline films for their widespread uses.The particular interest of this book Chapter Growth of Co-based magnetic thin films by magnetic fields MF assisted electrodeposition and heat treatment is the finding that the microstructure and magnetic properties of nanocrystalline Co-based alloys and oxides like CoX X= Cu, Ni, NiP, FeO are improved by imposition of MF during elaboration process or post-annealing process. "ccording to the previous study, the targeted scientific activities pay more attention to develop alloys and oxides in nanoscale using pulsed electrodeposition assisted by high magnetic field HMF . Note Since the instantaneous current density during pulse electrodeposition is higher than that during direct current plating, the microstructure of the nano-scale electrodeposits can be more easily controlled by perturbing the desorption/adsorption processes occurring in the pulse electrodeposition process .During the experiment, high magnetic field is an in-situ method for the control of electrodeposition process. The obtained material is then annealed or oxidized after