 The measurement problem is really a complex of problems, revolving around the question of whether one can apply quantum mechanics itself to the description of quantum measurements. One can just deny this, if one takes quantum mechanics to be a phenomenological theory. But if quantum mechanics is not the fundamental theory that explains the phenomenology of quantum measurements, the question arises how we can explain what ‘measurements’ and ‘results’ are. This is the measurement problem in the wide sense of the term.