I would like to trace the evolution of the major problems or questions since the 1950’s by showing several diagrams (Fig. 1a-e) based on my own recollections. As for the coordinates of the diagrams, the latitude towards North indicates the magnitude of surprise and that towards the South indicated is the deepening of our knowledge. Of course such a visual approach is incomplete and is full of personal prejudices, and many important subjects and considerations may be missing.

I will not go into detail of the interpretation of the diagram. But from the series of the diagram we may see that unification and diversification of the questions alternate as one of our co-panelists, Freeman Dyson, pointed out in one of his inspiring books.

In the 1970’s to the 1980’s we had good hopes that GUT would develop and in its evidence mono-poles and Proton-decay’s would be discovered and that proposed candidates of the dark matter may also be discovered from fairly reasonable particles to much more exotic particles.