ABSTRACT
To conclude such a topic as the one we have been addressing in this book is quite a hard task. It is probably the hardest part of the job but it is also the one which makes the whole enterprise worth the effort, as it is the part which will allow us, and hopefully the reader, to put all the achievements into a wider perspective, both in time (we think here of the future of our field) and, to some extent, in space (by which we mean other fields of physics).
