"As water freezes, it expands. Since cells are made up of mostly water, freezing expands the "stuff" inside which destroys their cell walls and they die. The cryonics companies need to remove and/or replace this water. They replace it with something called a cryoprotectant. Much like the antifreeze in an automobile. This glycerol based mixture stops and protects against your organs and tissues by hindering the formation of ice crystals. This process is called "vitrification" and allows cells to live in a sort of suspended animation.
After the vitrification, your body is cooled with dry ice until it reaches -202 Fahrenheit. After this pre-cooling, it's finally time to insert your body into the individual container that will be placed into a metal tank filled with liquid nitrogen. This will cool the body down to a temperature of around -320 degrees Fahrenheit.
The procedure isn't cheap. It can cost up to $200,000 to have your whole body preserved. For the more frugal optimist, a mere $60,000 will preserve your brain with an option known as neurosuspension. They hope the technology in the future will allow them to clone or regenerate the rest of the body."
And check out this facility in the US that regularly does this, it claims to have 112 people in Cryostasis, and 188 forms of DNA/tissue in Cryostasis.
http://cryonics.org/index.html