**About the Editors**

**Michael Fromm** is a senior professor and former Head of the Institute of Clinical Physiology at the Charite—Universit ´ atsmedizin Berlin, Germany, where he still works. He has published ¨ more than 230 research articles, resulting in an h-index of 61. Through this, he has made seminal contributions to transport mechanisms and barrier functions of intestinal and renal epithelia in health and disease. For some claudins, he has discovered that they form channels selective for ions and/or water. Starting in 2006, he was the coordinator of the Deutsche Forschungsgemeinschaft (DFG) Research Unit "Molecular structure and function of the tight junction", which paved the way to a currently running DFG graduate school focusing on tight junction research. Within this, his lab focuses on protein prerequisites of tricellular tight junction water permeability.

**Susanne M. Krug** has studied Biochemistry and is now a Group Leader at the Institute of Clinical Physiology at the Charite—Universit ´ atsmedizin Berlin, Germany. She has made remarkable ¨ contributions to the understanding of the tricellular tight junction as a regulated passage site for macromolecules, especially in inflamed intestinal epithelium. Presently, she holds three grants of the Deutsche Forschungsgemeinschaft (DFG) and, based on >60 publications, has reached an h-index of 25. Her current research interests still deal with tricellular tight junctions, but also with interaction of immune cells and tight junction proteins in inflammatory bowel diseases.
