Cryonics is the low-temperature preservation of humans and animals that can no longer be sustained by contemporary medicine until resuscitation may be possible in the future. Currently, human cryopreservation is not reversible, which means that it is not currently possible to bring people out of cryopreservation alive. The rationale for cryonics is that people who are considered dead by the current legal or medical definitions will not necessarily be dead by future standards â€“ the most stringent standard being the information-theoretic definition of death â€“ and that such people could be brought out of cryopreservation in the future.
In the United States, cryonics can only be legally performed on humans after they have been pronounced legally dead.
The word cryonics is derived from the Greek word ÎºÏÏÎ¿Ï‚ (kryos), meaning cold. Note that "cryonics" is often mistaken for the concept of suspended animation. Procedures similar to cryonics have been long featured in many examples of science fiction.
Cryonics is not a panacea for future immortality. Cryonics advocates point out that prognosis for cryonics patients is variable, with braindead patients having little chance of meaningful recovery even with foreseeable cryonics technology, while patients who are vitrified immediately after irreversible cardiac arrest is ascertained would fare the best. Most proponents of cryonics see it as a speculative medical technology, no different in principle from the defibrillator or advanced cardiac life support.