The two talks are based on R. Bott's paper "An application of the Morse theory to the topology of Lie groups" which is published in Bulletin de la Soc. Math. France, vol 84 (1956). If G is a given compact, connected and simply connected Lie group, then the adjoint action on G by itself is variationally complete. If N is an orbit of the adjoint action and P is a regular point away from N, then the space S(G, N) of all the geodesics from N orthogonally which end at P is the same as the space S(T, N'), where T is the maximal torus of G determined by P and N' is the intersection of N and T. By the exponential map from the the Cartan subalgebra t to the maximal torus T, the Morse series associated with S(T, N') can be read off from the diagram of G. If we consider the special case when N is the orbit of the identity element e of G, the Morse series associated with S(G,e) has no odd power. Then Poincare seires of the loop space of G is the same as the Morse series associated with S(G,e) as a consequence of Morse inequalities. As a corollary of this, the second homotopy group of G is zero and the third homotopy group is the ring of integers as long as G is a simple compact connected Lie group. For a special interest, the betti numbers of the exceptional Lie groups E_6, E_7, E_8 are computed by this method.