The present text grew out of a number of lecture courses for advanced under­ graduate and new graduate students in nuclear physics. They were given at summer schools in Leuven, Melbourne, and at study weeks for Dutch grad­ uate students which aimed to emphasize fundamental and topical aspects of nuclear physics. On occasion, part of the present text was presented to stu­ dents from a much wider field than just nuclear physics and also within a number of general physics colloquia, where, in addition to nuclear physicists, physicists from many other fields were present. In this respect, the intention is to present, in an amply illustrated form, the key quest ions that arise in nuclear physics. At the same time we try to show why a better understanding of the atomic nucleus is not only important in itself, but also yields essential insights into the many connections to other fields of physics. We thus concen­ trate on the unifying themes rather than addressing in great detail particular subfields of nuclear physics. The present project does not aim to be another comprehensive textbook on nuclear physics: Many of the detailed technical arguments that enter into the picture are not developed here as they would be in a more standard textbook. Instead they are presented using analogies, quite often with simple pictures and arguments that try to convey the general line of thinking and working in nuclear physics.