The discussion of particle-wave dualism still plays an important part in teaching quantum theroy. This surely is for historical reasons, since it was important in grasping the concept of uncertainty. Recent EPR-like experiments, however, indicate new ways of teaching the notions of uncertainty and complementarity. These allow us to achieve a clear understanding without difficult mathematical obstacles and promote also a well-founded discussion of philosophical aspects. The core of the considerations presented here are systems consisting of two-state objects, for example the spin states of photons or electrons.