Water is vital for life and how it freezes is very important. For years water (ice) has been known to exist in 15 phases. Subjected to higher pressures and varying temperatures, ice can form in fifteen separate known phases. With care all these types can be recovered at ambient pressure. The types are differentiated by their crystalline structure, ordering and density. There are also two metastable phases of ice under pressure, both fully hydrogen-disordered; these are IV and XII. Ice XII was discovered in 1996. In 2006, XIII and XIV were discovered. Ices XI, XIII, and XIV are hydrogen-ordered forms of ices Ih, V, and XII respectively. In 2009 ice XV was found at extremely high pressures and −143 degrees celsius. Now there is another variation.