Physics was often said to be the science of the 20th century, as it brought forward revolutions such as the theory of relativity and quantum physics. In particular quantum mechanics has been precisely confirmed in an uncountable number of experiments and without this theory we would not be able to understand the working principles of many modern devices that we use every day. On the other hand, quantum mechanics still challenges us with a number of fundamental questions: What is reality? What is the relation between objective randomness and determinism in the world? Is Aristotle's sentence of contradiction always valid or is it possible for an object to "be" and "not to be" in a given place at the same time? What "is" and what is only "knowable"?

Philosophical as these issues appear, some light can be shed on them in modern and conceptually simple experiments. And it turns out that our common view of reality seems often not to fit genuine quantum phenomena. We will discuss some possible answers to the question, why our macroscopic world appears so 'normal' although physics at the small scale is rather described by potentiality than reality. And we will sketch how one might exploit the intrinsic quantum ambiguity for possible applications in the field of nano-engineering.