From Singularity Hub, a piece on cryonics that you might not agree with all of, but is well worth the time to read: "Given the exponential rate of modern scientific innovation, cryonics suggests that new technologies may soon be available that can resurrect an individual considered 'dead' by today's standards. Because our personalities and memories have chemical foundations in the brain, they can hypothetically be preserved in the body, so long as neural tissue does not degenerate (as we'll see, that might be a logical jump). One way of preserving tissue is to store it at extremely low temperatures, effectively grinding your molecular chemistry to a halt. To put it bluntly, the cold keeps your body from rotting. But, as every high school student knows, your body is mostly water, which expands when frozen. This is where a process called vitrification enters the picture. Cryonics patients are preserved in vats of liquid nitrogen cooled to temperatures below -200°F. Because ice crystals can damage cells as they form, the water that fills our cells must be partially replaced before the body is cooled. Chemicals solutions called cryoprotectants are circulated through the patient's body, ultimately reaching a concentration greater than 50%. As the body is cooled, the cryoprotectants allow tissues to reach a glass-like solid state that is relatively free of ice crystals, thus preserving cellular integrity." You might also want to look at Alcor's FAQ for Scientists.