Cryonics is the low-temperature preservation of humans and other animals that can no longer be sustained by contemporary medicine until resuscitation may be possible in the future. Human cryopreservation is not currently reversible. In the United States, cryonics can only be legally performed on humans after pronounced legally dead. The rationale for cryonics is that the process may be reversible in the future if performed soon enough, and that cryopreserved people are not dead by the modern information-theoretic definition of death. Cryonics is derived from the Greek word ????? (kryos), meaning icy cold. There is a high representation of scientists among cryonics supporters. Scientific support for cryonics is based on studies showing substantial preservation of brain cell structure by current methods, and projections of future technology, especially molecular nanotechnology and nanomedicine. Some scientists believe that future med