cryosleep

Cryosleep, also called cryogenic sleep or suspended animation, refers to cooling and preserving a living organism at cryogenic temperatures with the aim of stopping biological processes for extended periods. In contemporary practice, cryosleep for humans is speculative science; cryonics is a related field that preserves legally dead individuals at low temperatures in the hope of future revival.

Current procedures in cryonics emphasize rapid stabilization after legal death, followed by cooling and immersion in liquid nitrogen. To reduce ice-related damage, cryoprotective agents are used, and tissues are carefully vitrified to avoid ice crystal formation. Long-term preservation then occurs at approximately -196°C in specialized dewars with ongoing monitoring and custody.

Concepts of long-term preservation gained prominence in the 20th century, with writers and researchers proposing suspended life for space travel, medical treatment, or postponement of aging. Organizations such as the Alcor Life Extension Foundation and the Cryonics Institute currently maintain cryopreserved patients, funded by member dues and donations, within a regulatory and ethical gray area in many jurisdictions.

There is no demonstrated method to revive a cryopreserved human. Technical challenges include tissue and neural integrity after freezing, restoration of metabolism, and addressing accumulated damage. While research in vitrification, nanotechnology, and future repair approaches has been explored, cryosleep remains speculative and not an established medical treatment. Practical use is generally discussed in the context of science fiction and future technologies.