Modern science rests on a sophisticated interplay between theory and experiment. The way in which this interplay extends physical reality beyond the observable realm gave rise to the conflict between Galileo and his Aristotelian opponents and it has been nurturing the later debates on scientific realism up to today. In order to get a better understanding of the problems involved in the debate about subatomic reality, this interplay has to be analyzed in more detail. In particular, the constructive features of modern physics have to be investigated. The classical construal of subatomic reality turned out to be too strong. This is a point in favor of constructivism (even though as a philosophical position, constructivism cannot cope with the empirical successes of modern physics and the self-correction mechanisms inherent in theory formation).