Quantum Theory, namely the theory where Information and Physics meet

After more than a century since its birth, Quantum Theory still eludes our under1 standing. If asked to describe it, we have to resort to abstract and ad hoc principles about 2 complex Hilbert spaces. How is it possible that a fundamental physical theory cannot be de3 scribed using the ordinary language of Physics? Here we offer a contribution to the problem, 4 providing a short non-technical presentation of a recent derivation of Quantum Theory from 5 information-theoretic principles [1]. The picture emerging from the principles is that Quan6 tum Theory is the only theory of information compatible with the purity and reversibility of 7 physical processes. 8