This is probably inevitable after a major experimental breakthrough, and so it was time to bring together experimentalists and theoretists to discuss which had been the main achievements of the last years and to try to find out which will be the development in the future. This Conference was hosted by the IBM Scientific Center at the Universidad Autonoma of Madrid to provide a forum in which this discussion could take place. As such, the emphasis was on the interpretation of known results. Nevertheless, much new material is covered in these Proceedings.