I want to talk to you about one application of my early work on these electronic excitations, followed by vibration. One work which I believe is quite amusing in connection with one of the classical problems of the structure of molecules. I am talking about benzene. What is benzene? Six carbon atoms in an exact hexagon with six hydrogen atoms hanging out, again same six-fold symmetry, all in a plane. The classically accepted formula for that molecule was something a little peculiar. Not one formula but two. Of the six carbon atoms, the six carbon atoms are alternately connected with single bonds repres- representing a pair of electrons and double bonds representing two pairs of electrons. Now, this you can do, obviously, in two ways. Double bond, single bond, double bond, single bond, double bond, single bond, back to double bond. Or the opposite. Single bond, double bond, single bond, double bond, single bond, double bond, single bond.