This article is protected by German copyright law. You may copy and distribute this article for your personal use only. Other use is only allowed with written permission by the copyright holder. Z. Phys. Chem. 223 (2009) 939–956 . DOI 10.1524.zpch.2009.6064 © by Oldenbourg Wissenschaftsverlag, München Review paper Understanding Static and Dynamic Heterogeneities in Confined Water By H. Eugene Stanley * Center for Polymer Studies and Department of Physics, 590 Commonwealth Avenue, Boston University, 02215 Boston, MA, USA Dedicated to Prof. Dr. Alfons Geiger on the occasion of his 65 th birthday (Received July 24, 2009; accepted July 26, 2009) Confined Water . Widom Line We report recent efforts to understand the new MIT-Messina experimental discovery of a dy- namic crossover at low temperatures in confined water. Preliminary calculations are not incon- sistent with one tentative interpretation of this dynamic crossover as resulting from the system passing from the high-temperature high-pressure "HDL" side of the Widom line (where the liquid might display fragile behavior) to the low-temperature low-pressure "LDL" side of the Widom line (where the liquid might display strong behavior). The Widom line - defined to be the line in the pressure-temperature plane where the correlation length has its maximum - arises only if there is a critical point. Hence interpreting the MIT experiments in terms of a Widom line is of potential relevance to testing experimentally, for confined water, the liquid-liquid critical point hypothesis. 1. Introduction This author's water research began 30 years ago - when, under the auspices of a Guggenheim Fellowship, he learned "the facts of water" under the tutelage of three mentors, J. Teixeira, A. Geiger, and C. A. Angell. The most puzzling facts dealt with understanding what are the various experimentally-observed cross- overs and non-monotonic behavior telling us about the underlying physics and chemistry of water. How can we understand the observed facts that as one cools below 46 ° C and 35 ° C, respectively, the volume and entropy fluctuations (com- * Corresponding author. E-mail: hes@bu.edu