Previously microstructures have been characterized by a rather abstract point of view, whose free energy, which satisfies the principle of material indifference, depends in a very general way on a not exactly established number of variables. We point out that also in the case of large deformations it is possible to conceive physical models of microstructures which admit a free energy of the type previously considered. For this purpose, in this first lecture the necessary premises of a kinematic and geometrical type are established.