Escaping the no man's land: Recent experiments on metastable liquid water

The properties of supercooled water have been the subject of intense studies for decades. One of the main goals was to follow the evolution of water anomalies, already present in the stable liquid, as far as possible in the metastable phase. All anomalies were found to become more pronounced, but their origin has hitherto remained hidden because of crystallization into ice. We review the recent experimental developments in the field, with a focus on the techniques used to reach a larger metastability, or to extend the investigations to the negative pressure region of the phase diagram, where the liquid is also metastable with respect to its vapor.