Reviving people frozen after death

How far away is reviving people who have been frozen after death?

Cryonics stores people at very low temperature after legal death, in the hope that future medicine can revive them. In the sources reviewed, no cryopreserved human or whole mammal has been revived, and no study has shown that memory or identity survives storage. Work on organs is further along: vitrified rat kidneys were stored for up to 100 days and restored life-sustaining function after transplant. Mouse brain slices recovered neuronal excitability and basic synaptic transmission after vitrification and rewarming, but that work was done on slices and not on whole brains in a body.

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WHERE WE AREScience unproven

Very far away. The basic science has not been shown to work.

Vitrification and rewarming have been shown in rat kidneys that worked after transplant, and in mouse brain slices that showed activity after rewarming. Preserved brain structure has been shown in animals, but that is not the same as revival. In the sources reviewed, no cryopreserved human or whole mammal has been revived, and no study has shown that memory or identity is kept through storage. The step that cryonics depends on, reviving a whole body, has not started, so the stage is science-unproven. The stage would change only if a whole mammal were revived after cryopreservation and its function tested.

The tech tree

Everything recorded on Vrulum that this future needs, oldest foundations at the top and the goal at the bottom. Lines show what each step requires.

What it takes: Reviving people frozen after death Unlocked Being researched Locked
  1. 1985Organ and tissue cryopreservationResearch and prototypes Being researched.
  1. 2016Vitrification of human embryos in assisted reproductionDone Unlocked.
  2. 2018Whole pig and rabbit brains preserved with synaptic structure intactDone Unlocked.
  3. 2023Vitrified rat kidneys rewarmed and transplantedDone Unlocked.
  4. 2026Vitrified mouse brain slices show activity after rewarmingDone Unlocked.
  5. Date not recordedHuman brain biopsies analysed after rewarmingIn progress Being researched.
  6. Date not recordedWhole mammal revived after cryopreservationNot started Locked.
  7. Date not recordedMemory and identity kept through storageNot started Locked.
  8. Date not recordedRewarming a whole human bodyNot started Locked.
  9. Date not recordedRepairing freezing and chemical damageNot started Locked.
  1. GoalReviving people frozen after deathGoalRequires: Organ and tissue cryopreservation, Vitrified rat kidneys rewarmed and transplanted, Vitrified mouse brain slices show activity after rewarming, Whole pig and rabbit brains preserved with synaptic structure intact, Vitrification of human embryos in assisted reproduction, Human brain biopsies analysed after rewarming, Whole mammal revived after cryopreservation, Memory and identity kept through storage, Rewarming a whole human body, Repairing freezing and chemical damage. Locked.

The road so far

4 of 9 steps done, 1 in progress.

  1. Done · 9 Jun 2023Vitrified rat kidneys rewarmed and transplanted

    Han and colleagues vitrified rat kidneys, stored them at −150 °C for 1 to 100 days, and rewarmed them by nanowarming, with a radiofrequency field applied to heat the warming agent. All five nanowarmed kidney recipients, and all five fresh-kidney controls, survived the 30-day follow-up. The authors report initial graft dysfunction for about 2 to 3 weeks in the nanowarmed group. The work used rats only, with 4 to 8 animals per group, and recipients were followed for 30 days only. [1]

  2. Done · Mar 2026Vitrified mouse brain slices show activity after rewarming

    A team at Friedrich-Alexander-Universität Erlangen-Nürnberg, led by Alexander German, vitrified mouse hippocampal slices and reported recovery of membrane integrity, synaptic structure, neuronal excitability and basic synaptic transmission after rewarming, as reported by ZME Science. In whole-brain attempts, only one of three brains was in good enough condition for functional testing. ZME Science reports that the work does not show anything close to reviving an animal, let alone a person. [3]

  3. Done · Mar 2018Whole pig and rabbit brains preserved with synaptic structure intact

    The Brain Preservation Foundation awarded its Small Mammal prize in February 2016 for a whole rabbit brain preserved with aldehyde-stabilised cryopreservation and checked by 3D electron microscopy. It awarded its Large Mammal prize in March 2018 for synaptic connectivity across an entire pig brain. The foundation states that the researchers did not revive a pig or a pig brain, and that glutaraldehyde fixation leads to death by contemporary standards and makes biological revival impractical. Both results are the foundation's own announcements. The foundation says the 2018 result was a single laboratory demonstration and is not enough to meet the quality control expected for human use. [5][6]

  4. Done · 4 Nov 2016Vitrification of human embryos in assisted reproduction

    A systematic review and meta-analysis by Rienzi and colleagues pooled seven randomised trials covering 3,615 embryos. Vitrification gave better embryo survival after warming than slow freezing (relative risk 1.59, 95% CI 1.30 to 1.93). The clinical pregnancy result was borderline (relative risk 1.89, 95% CI 1.00 to 3.6), and the authors rated the clinical-outcome evidence as low quality. This shows that vitrification works for early embryos in assisted reproduction, not that it works for whole bodies. [2]

  5. In progressHuman brain biopsies analysed after rewarming

    Greg Fahy analysed biopsies from the brain of L. Stephen Coles, a gerontologist who died in 2014 and whose brain was cryopreserved at Alcor, where it has been kept at about −146 °C. Fahy reports that rewarmed and rehydrated brain cells regained some of their original structure. The work is an unreviewed preprint. MIT Technology Review states that there is no evidence the cells could regain electrical activity or a functioning metabolism. [4]

  6. Not startedWhole mammal revived after cryopreservation

    No cryopreserved whole mammal has been revived. The Brain Preservation Foundation says its pig brain result did not revive the animal. The 2026 mouse slice study does not show anything close to reviving an animal after freezing. [6][3]

  7. Not startedMemory and identity kept through storage

    No study has shown that identity, memory or consciousness can be stored and restored in a whole, frozen animal. MIT Technology Review reports that Shannon Tessier said brains already in storage have not been validated to work for reanimation. [3][4]

  8. Not startedRewarming a whole human body

    No whole human body has been cooled to cryogenic temperature and rewarmed for revival. Rewarming so far has been tested on rat kidneys, on mouse brain slices, and on human brain biopsies. In the 2026 mouse study, only one of three whole brains was in good enough condition for functional testing. [3][1]

  9. Not startedRepairing freezing and chemical damage

    In the sources reviewed, no method has been shown to repair damage from cryoprotectants, ice formation, or the chemical fixatives used in aldehyde-stabilised preservation. Matthew Powell-Palm, quoted by MIT Technology Review, says that neurons could be damaged in many ways. The Brain Preservation Foundation states that the glutaraldehyde step is irreversible. [4][6]

Why it matters

Organ vitrification could one day allow donor organs to be stored for much longer than cold storage allows, which would ease transplant logistics. Cryonics raises a different question: whether a person who has been legally declared dead could later be restored. The science for that is not yet in place, so the practice rests on hope rather than demonstrated results. Greg Fahy, quoted by MIT Technology Review, says that restoring function to a preserved brain is a separate question from preserving its structure.

What stands in the way

  • No cryopreserved human or whole mammal has been revived, and no method is shown to restore function after storage.
  • Large tissues are hard to vitrify and rewarm. ZME Science reports that larger brains and organs present major barriers to any human application. In the 2026 mouse study, only one of three whole brains was in good enough condition for functional testing.
  • The best-preserved brain results rely on glutaraldehyde fixation, which the Brain Preservation Foundation says causes death by contemporary standards and cannot be reversed.
  • The rat kidney study covers 30 days of follow-up, uses small groups, and tests storage only up to 100 days.
  • Storage has not been shown to keep memory, identity or consciousness, and no tests of these have been reported for a whole frozen animal.
  • MIT Technology Review reports that stored brains have not been validated to work for reanimation.

Signals to watch

  • A whole small mammal vitrified, rewarmed and tested for behaviour and brain function after survival.
  • Nanowarmed kidney transplants in a large animal, with follow-up well beyond 30 days.
  • Peer-reviewed publication of the human brain biopsy study, including whether electrical activity or metabolism were tested after rewarming.
  • Whole-brain vitrification studies that test function across cell types, not only in one brain region.
  • Guidance from cryobiology societies or regulators on human use of cryopreservation after death.

Sources

  1. peer reviewed paper
    Vitrification and nanowarming enable long-term organ cryopreservation and life-sustaining kidney transplantation in a rat model
    Zonghu Han, Joseph Sushil Rao, Lakshya Gangwar et al.. Nature Communications, 9 Jun 2023.
  2. review article
    Oocyte, embryo and blastocyst cryopreservation in ART: systematic review and meta-analysis comparing slow-freezing versus vitrification to produce evidence for the development of global guidance
    Laura Rienzi, Clarisa Gracia, Roberta Maggiulli et al.. Human Reproduction Update, 4 Nov 2016.
  3. news
    Mouse Brain Tissues Recover Key Activity After Deep Freeze, but Cryonics Remains Far Off
    Tudor Tarita. ZME Science, 23 Mar 2026.
  4. news
    This scientist rewarmed and studied pieces of his friend's cryopreserved brain
    Jessica Hamzelou. MIT Technology Review, 24 Mar 2026.
  5. other
    Small Mammal BPF Prize Winning Announcement
    Brain Preservation Foundation (prize organiser's announcement), Feb 2016.
  6. other
    Large Mammal BPF Prize Winning Announcement
    Brain Preservation Foundation (prize organiser's announcement), Mar 2018.

Last reviewed 21 Oct 2026.