The four lectures presented in this volume discuss recent ideas such as bifurcation, catastrophe and singular theory in elastic post-buckling but avoid advanced mathematics. The influence of imperfections and boundary conditions on the maximal load of stiffened shells of revolution is studied by numerical methods. Experimental methods to test compressed structures are presented and will serve as a useful guide for engineers and physicists. Also of practical importance is the thorough discussion of the state of the art in plastic buckling of plates and shells under the influence of the constitutive laws. The lectures are intended for postgraduate students, but at the same time they should serve as a review for researchers and engineers in solid mechanics.