**Highlights**


**Author Contributions:** All the authors (D.G., N.B., F.M.U., and R.C.) participated in the development of the ideas for this review, contributed to reading the articles, and to the writing and editing the manuscript.

**Funding:** The research activity of D.G. and N.B. is supported, in part, by grants of Italian Government ("5 per mille 2017" and "Ricerca Corrente 2018–2020").

**Acknowledgments:** We acknowledge Gerald Goldsmith for his valuable assistance in revising the English language.

**Conflicts of Interest:** The authors declare no conflict of interest.
