Ferromagnetic materials are widely used in our life and could be seen in many technological applications. As a result, it is important to have a deep understanding of their intrinsic properties. The Kerr effect originating from the slight rotation of the polarization plane of incident light when it is reflected from the surface of a ferromagnetic material provides useful information about the material. In the first part of the project, a Magneto-Optical Kerr Effect (MOKE) microscope was constructed and tested on ferromagnetic materials. In the second part, four samples made of [Co/Ni(t)/Co/Pt]x4 multilayers with different thicknesses of Nickel were investigated using the setup. The evolution of magnetic domains was investigated as a function of time for a fixed applied magnetic field. Both static and dynamic studies on ferromagnetic materials are then possible with MOKE microscope. At the end of the project, a comparison of the magnetic properties of these four samples with two reference samples (Co/Ni)x8 and (Co/Pd)x8 were presented.