What Is Cryonics and How Does It Work?

The Idea Behind Cryonics

Imagine being frozen at the moment of death, then thawed centuries later when medicine has advanced far enough to cure whatever killed you. That is the premise of cryonics — the low-temperature preservation of human remains in liquid nitrogen at −196 °C (−321 °F), in the hope that future technology will make revival possible.

The idea entered mainstream consciousness through physicist and educator Robert Ettinger, whose 1964 book The Prospect of Immortality argued that science would eventually be capable of repairing any damage caused by death and freezing. The first person to be cryonically preserved was Professor James Bedford, a cancer patient who was frozen in January 1967 and whose body remains stored at the Alcor Life Extension Foundation in Scottsdale, Arizona to this day.

The Preservation Process

Cryonics does not simply mean putting a body into a freezer. The process is technically complex and must begin within minutes of legal death to limit cellular damage.

Step 1: Stabilization

As soon as a patient is declared legally dead, a standby team begins cardiopulmonary support — pumping oxygenated blood to the brain — while the body is cooled with ice to slow metabolic processes. This buys time for the next critical stage.

Step 2: Cryoprotection

Plain water inside cells is the enemy. When water freezes, it expands by roughly 9% and forms sharp ice crystals that shred cell membranes. To prevent this, cryonics providers use a process called vitrification: the blood and water in the body are gradually replaced with a cocktail of cryoprotectant chemicals — substances such as dimethyl sulfoxide, ethylene glycol, and propylene glycol that prevent ice formation. Instead of crystallising, the tissues transition into a glass-like, amorphous solid as temperature falls, which is far less damaging.

Step 3: Cooling and Storage

The body is cooled slowly to around −130 °C, the glass transition temperature at which biological activity halts completely. It is then placed in a large vacuum-insulated dewar flask filled with liquid nitrogen at −196 °C, where it can theoretically remain in a state of complete biological pause indefinitely. Liquid nitrogen requires no electricity — it simply needs to be topped up weekly.

Who Offers Cryonics Today?

As of the mid-2020s, roughly 500 individuals are cryonically preserved worldwide across five facilities: three in the United States, one in Russia, and one in Germany. The two largest U.S. providers are Alcor, which charges around $200,000 for whole-body preservation or $80,000 for neuropreservation (head only), and the Cryonics Institute, whose plans start at around $28,000. Many members fund the cost through a dedicated life insurance policy.

Some members opt for neuropreservation on the assumption that the brain holds all of the information that constitutes personal identity, and that a future revival could involve growing or building a new body.

What Scientists Say

The mainstream scientific community is deeply skeptical. Cryonics is widely characterised as a pseudoscience, with critics arguing that current preservation methods inevitably cause severe, irreversible damage — particularly to the complex neural circuitry of the brain. Large vitrified tissue masses also tend to develop fractures as they cool, a problem that worsens with the sheer volume of a whole human body.

Some researchers acknowledge a more nuanced position. Laboratory advances in nanowarming — using radio-frequency-excited iron oxide nanoparticles to thaw tissue uniformly from the inside out — have successfully preserved whole rat organs with intact cell structure, according to work from the University of Minnesota. But as the MIT Technology Review noted, none of these developments provide a clear path to reviving a whole human being.

The central legal and scientific problem is also definitional: by the time a cryonics team can act, the patient is already legally dead, meaning some degree of ischemic brain damage has almost certainly occurred before preservation even begins.

A Bet on the Future

Cryonics proponents frame the practice not as a proven medical procedure but as a calculated gamble — the argument being that the small probability of future revival outweighs the certainty of decomposition. Critics counter that it exploits vulnerable people facing death with promises science cannot currently back up.

Whether cryonics ever crosses from fringe aspiration to medical reality depends on breakthroughs that do not yet exist: reliable large-scale vitrification, nanoscale tissue repair, and a far deeper understanding of how identity and memory are encoded in the brain. For now, those preserved in liquid nitrogen are in a state of waiting — for science to catch up, or not.