Helium in its solid form has a crystalline structure and sharp melting point. It is the only element that cannot be solidified using low temperatures at ordinary pressures. It changes to solid form when compressed to a pressure of 25 bar atmospheres at a temperature of ?457 degrees Fahrenheit.
Helium remains liquid down to absolute zero temperature in its normal state and has two forms: helium I (He4I) and helium II (He4II). Both helium I and II are quantum fluids displaying atomic properties on a macroscopic scale due to their boiling point being close to zero. The freezing point of helium is also low compared to all other elements.