Multiple Phases of Liquid Water

The history of the study of the anomalies of liquid water, from the 17th century up to the present, is reviewed and the current view on the origin of these anomalies is summarized. The hypothesis of the multiple liquid-liquid transitions of water in the supercooled region is consistent with the available experimental and simulation data and provides physical explanation of water behavior in a wide thermodynamic range. The general character of the liquid-liquid transitions of fluids is discussed and the remaining questions are formulated.