The nitrogen is used in both liquid and gas form in our microelectronics lab where we manufacture thick and thin film integrated circuits. The dewar shown holds enough nitrogen to last the lab about three weeks of operation. It is essentially an overgrown thermos flask consisting of an inner and outer shell with vacuum in between. The fog is generated from water vapour in the surrounding air and from large amounts of nitrogen liquid which are boiling away into the environment. For our demo the liquid nitrogen is poured into a beaker.
Vapour is seen as the cold liquid cools the beaker and surrounding air.
When a balloon containing air is placed into the liquid nitrogen the balloon contracts as air inside is liquified. Nitrogen and oxygen in the air turn to liquid.