What happens when you put liquid nitrogen in a vacuum chamber? It turns solid. And then it snows. As the vacuum lowers the pressure in the chamber, it decreases the boiling point of the liquid nitrogen which means the nitrogen boils faster. But! The boiling liquid nitrogen is also evaporating which cools itself, which turns the liquid nitrogen so cold that it turns into a solid. Solid nitrogen colder than -346 degrees Fahrenheit.
What's even cooler is that once the liquid nitrogen becomes solid, there's another step after that. The video from Chef Steps shows how the nitrogen wants to re-organizes itself into something more tightly packed, which kicks off a sweet chain reaction with a bit of snowfall: