I have presented a Ph.D. thesis in cardiac cellular electrophysiology: these four years of training gave me a good insight into the cellular and molecular electrophysiology and pathophysiology. At this moment, I am in training as a cardiologist, with a special focus on clinical electrophysiology. If I want to bridge the gap between both fields (as expressed above), I need more insight into the mechanisms and characteristics of reentrant circuits, that are responsible for most arrhythmias. This includes 1) detailed mapping techniques to identify the particular circuits in different types of arrhythmias, and 2) a better understanding of the conceptual ideas about reentrant circuits and about their interaction with antiarrhythmic drugs and pacing.