Fifty years of quantum mechanics

After a brief historical survey of successful applications of non-relativistic quantum mechanics to atomic and molecular physics as well as to the solid state physics it is pointed out that a true reconciliation with the theory of relativity may be achieved only within the framework of quantum field theory. The formalism of quantum mechanics being no more controversial, almost perfect, there are still severe discrepancies of opinions in the subject of probabilistic interpretation. Arguments are given in favour of the assumption that quantum mechanics applies to single systems of the microscopic world and not necessarily to ensembles. (author)