Cryonics is the practice of freezing clinically dead people in liquid nitrogen with the hope of future reanimation. Advancednanotechnology or mind uploading are the favored prospects for implementing the "and then a miracle occurs" stage, which is currently everything that follows the initial freezing.
Scientists will admit that some sort of cryogenic preservation and revival does not seem to violate known physics. But they stress that, in practical terms, freezing and reviving dead humans is so far off as to hardly be worth taking seriously, and current cryonics practice is speculation at best and quackery and pseudoscience at worst.
