An autofill freezer requires being connected to a liquid nitrogen supply. Storage tanks use vacuum insulation to hold liquid nitrogen. There is a special cryogenic hose that runs from the supply tank to the freezer. The freezer has a microprocessor that controls the liquid levels via sensors and a solenoid valve. Samples can be stored submerged in the LN2 liquid (called liquid phase storage) or have the samples stored above the liquid (called vapor phase storage).