The last half of the 19th century. Century was a lush time in physics. A number of theories had been erected and verified, and many believed that there was not much more to come after. But exactly in the year 1900 began a development which should turn up and down our perception of reality. Planck's discovery of the light's quantization was continued by Einstein in 1905 and Bohr in 1913 and led in 1925 to the formulation of quantum mechanics we still use. Already shortly thereafter, it became clear that quantum mechanics possessed quite unexpected properties that were very alien to the Newtonian world view. Today we have learned to live with this "quantum weirdness" and builds appliances, e.g. quantum computers that utilize it. It is paradoxical that we have no immediate intuitive understanding for the most fundamental aspects of the reality that we ourselves are part of.