Cooking with Liquid Nitrogen

I was watching the travel channel today and I saw a chef cooking with liquid nitrogen. I became curious at how liquid nitrogen could be useful in the kitchen. Liquid nitrogen has a saturation temperature of -321 F. It instantly freezes any food that it comes into contact with in the kitchen, which can cut down on time that a food would have had to spend in the freezer. Also, chef's use the fact that -321 F is much lower than any ambient temperature and the liquid nitrogen quickly evaporates in the form of a dense fog that can be used for dramatic effects in the food presentation.