Manganites oxides are of great interest in material sciences for the variety of physical properties they exhibit in connexion with possible long range spin, charge and orbital ordering. We propose a WISH experiment to investigate the structural and magnetic behaviours of CaMn4O8, for which the room temperature structure only is known. It can be described like a complex network of MnO6 octahedra connected by edges or corners, involving thus several types of magnetic interactions. As two magnetic transitions are observed on the magnetization curves at 100 and 50K, we will solve the spin configuration as a function of temperature. These results will be correlated with macroscopic magnetic and electrical properties , looking for magneto-electric coupling.