This book presents, in a variational form, very many two dimensional models which have been developed to overcome some weaknesses of the Kirchhoff-Love and Reissner-Mindlin's models. More precisely the N-T and N models are particularly treated because they clearly show the impact of the change in the third fundamental form whose contribution to the strain energy becomes important when the characteristic ratio of the shell is roughly greater than 0.3. Transverse stresses through-the-thickness are calculated. Gradient Recovery and Strain deformation approach with Curve triangular and Shifted Lagrange elements are implemented. These new FEM appear to be memory less greedy. .