Superposition

Intuitive

In some sense, the portrait Mona Lisa shows a superposition of cheerfulness and sadness. See Mona Lisa - ineffable smile of quantum mechanics by Slobodan Prvanovic

Concrete

In this section things should be explained by analogy and with pictures and, if necessary, some formulas.

Abstract

The motto in this section is: the higher the level of abstraction, the better.

Why is it interesting?