Water in a crowd.

In many situations, form biology to geology, water occurs not as the pure bulk liquid but rather in nanoscopic environments, in contact with interfaces, interacting with ionic species, and interacting with large organic molecules. In such situations, water does not behave in the same manner as it does in the pure bulk liquid. Water dynamics are fundamental to many processes such as protein folding and proton transport. Such processes depend on the dynamics of water's hydrogen bonding network. Here, the results of ultrafast infrared experiments are described that shed light on the influences of nanoconfinement, interfaces, ions, and organic molecules on water hydrogen bond dynamics.