**5. Conclusions**

The editors are grateful to the many authors, from ten countries, who contributed to this volume. We hope this will stimulate more investigation, including scientific drilling, and discussion of the magma–hydrothermal connection. Much remains to be done to combine and reconcile the insights of volcanologists, igneous petrologists who study plutons, and geothermalists, to understand the magma–hydrothermal regime as a single system.

**Funding:** This research received no external funding.

**Acknowledgments:** We thank Richard Li of MDPI/*Geosciences* for suggesting the magma–hydrothermal theme for a special issue.

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