You'll find a good essay on the history, practice and science of cryonics over at Kuro5hin. "Together, function and structure allow for life. Cryonics does not preserve all biological functions - vital functions like brain activity and heart-beat are over when modern medicine pronounces a person dead. But cryonics does preserve structure, and this is what makes it so important as a life-saving procedure. It may seem fanciful that death can be stopped as a result of cryonics, but the practice has scientific support." Cryonics is an experiment with an uncertain chance of success - but it is the best option open for the unfortunate millions who will die from age-related degeneration before real anti-aging medicine can be developed and deployed.