Cryonics (from Greek κρύος ‘kryos-‘ meaning ‘cold’) is the low-temperature preservation (usually at −196°C) of people who cannot be sustained by contemporary medicine, with the hope that resuscitation and restoration to full health may be possible in the far future. Cryopreservation of humans is not reversible with present technology; cryonicists hope that medical advances will someday allow cryopreserved people to be revived.
Cryonics is regarded with skepticism within the mainstream scientific community and is not part of normal medical practice. It is not known if it will ever be possible to revive a cryopreserved human being. Cryonics depends on beliefs that death is a process rather than an event, that clinical death is a prognosis of death rather than a diagnosis of death, and that the cryonics patient has not experienced information-theoretic death. Such views are at the speculative edge of medicine.
Cryonics procedures can only begin after legal death, and cryonics “patients” are considered legally dead. Cryonics procedures ideally begin within minutes of cardiac arrest, and use cryoprotectants to prevent ice formation during cryopreservation. The first corpse to be cryopreserved was that of Dr. James Bedford in 1967. As of 2014, about 250 bodies were cryopreserved in the United States, and 1,500 people had made arrangements for cryopreservation after their legal death.