First, I wish to express my appreciation of the honour implied by the dedication to me of the proceedings of this Colloquium. It is, of course, gratifying that colleagues should wish to make such a gesture, but I can think of many others in the field, many participants in this meeting, who are at least as worthy of a similar honour. I can only be grateful that the Scientific Organizing Committee chose me. I would also like to thank both it and the Local Organizing Committee, on your behalf as well as my own, for all the hard work that has made this Colloquium possible. I know enough of organizing meetings to guess at what has been involved in making this one run so smoothly. I have organized both IAU Colloquia and a meeting of the AAS, but I have never tried to do the two within three months of each other, as our hosts have done on this occasion!