Nitrogen molecules don't "like" to be near one another; they stay gas form unless they are VERY COLD.  You don't need much heat to get Liquid Nitrogen to boil:  it has to be at -195 degree C or lower to be a liquid!

Here is is boiling even as I pour it.  To liquid Nitrogen, room temperature is very hot.
 
 

Even in a thermos, the liquid Nitrogen boils, filling the glove above it with Nitrogen vapor.  Do we have to worry about this gas? About 78% of the air is Nitrogen, so there's no problem breathing it, so long as we get plenty of Oxygen as well.  When I travel to schools with liquid Nitrogen, I always leave my windows cracked to make sure plenty of Oxygen is getting in to the car.
 
 

Putting a balloon into liquid Nitrogen causes the air in it to get so cold, the Nitrogen actually condenses.  We get liquid Nitrogen in the balloon instead of Nitrogen gas, and the balloon deflates. (There is much less volume in the balloon, since the "liquid air" inside the balloon takes up so much less space than the gaseous air did.)  Once you take the balloon out of the liquid Nitrogen, the "liquid air" inside it will boil and blow up the balloon again.
 

Many people ask about what DRY ICE is.  Dry ice is solid Carbon Dioxide.  It turns out that if you get Carbon Dioxide gas cold enough it will freeze.  This solid Carbon Dioxide can go right from a solid to a gas form (known as "sublimation") so the ice is "dry".  Take a piece of dry ice and put it under water and it bubbles rapidly as it goes from solid to gas. By the way, snow can sublimate too, going right from solid to gas without ever melting. That is why snow can disappear even if it is below freezing.