From Longevity Wiki

Cryonics is the practice of preserving a human body at ultra-cold temperatures for multiple years, with the intention of restoring good health if that is made possible by future medical technologies.[1][2][3]

The patient long term care bay at Alcor Life Extension Foundation, circa 2020.

Cryonics is considered an experimental procedure. It is not yet possible to revive an adult human being from cryopreservation, and it is unknown if revival will ever become possible. There has been controversy within the scientific community regarding the technical feasibility of cryonics resuscitation, with support or skepticism from various scientists. If cryonics resuscitation becomes possible in the future, it would likely require advanced technologies such as molecular level repair, and detailed tissue regeneration.[4]

The first human cryopreservation was performed on Dr. James Bedford in January 1967.[5] As of 2020, there are about 390 individuals cryopreserved around the world, and about 3,100 people hold contracts with cryonics service providers to be cryopreserved immediately after their legal death.[6][7] Major cryonics storage companies include the Alcor Foundation and the Cryonics Institute in the USA, and KrioRus in Russia. A network of other cryonics organizations provide standby and stabilization services, local emergency response, cryonics information and outreach, and fundamental or applied research. There is some overlap between the goals of the cryonics field, and the wider organ cryopreservation and life extension fields.[8][9]

Conceptual Foundation


The practice of cryonics is based on a combination of current scientific understandings (knowns) and future technological possibilities (unknowns). Some of the concepts affecting the feasibility of cryonics are further described in later sections.

People choose to use cryonics services in the hope that their legal death will be temporary instead of permanent.[1][2][3] They would like to be revived at a future date and restored to good health, if that is made possible by future medical technologies. The use of advanced technologies to revive a person from a cryopreserved state may or may not become feasible, for reasons discussed here.

It is known that life can be stopped and restarted using very cold temperatures in some organisms.[10][11][12] it is known that for large organisms, the currently applied cooldown and rewarming processes cause varying amounts of tissue damage. An educated guess can be made about the types of tissue damage that are sustained in any particular human cryopreservation case. The amounts of damage can vary greatly depending on the cryopreservation timelines, and the techniques applied.[13] The amounts of neurological damage cannot be quantified in detail using current technology, because our understanding of the neurological basis of the mind is incomplete, and because we do not know the capabilities of future medical repair technologies.[14] Specifically, the mechanisms and systems by which personality and memory are physiologically encoded within the nervous system are not yet fully understood.[15]

In principle, a sufficiently advanced medical technology could repair some or all of the tissue damage caused by current cryopreservation technologies.[16][17] The detailed repair of an organism or human being at the cellular and molecular scales does not conflict with any known scientific principles. However, scientific possibility does not necessarily mean that comprehensive repairs will become feasible. There are significant engineering challenges involved with the development of medical technologies that would be capable of detailed tissue repair throughout a whole organism. Future technologies can currently be envisioned which involve molecular repair by nanomedicine, highly advanced computation, detailed control of cell growth, and tissue regeneration.[4] The trend for medical technologies to become more advanced over historic time frames increases the optimism that cryonics could work, but the historic trends do not guarantee success.[18][19]

Concepts Affecting the Feasibility of Cryonics

Known: Life can be stopped and restarted using very cold temperatures, in some organisms.

It's known that life can be stopped and restarted using very low temperatures in some organisms, as long as small scale biological structures are preserved. The cryopreservation and revival of a variety of species of whole small organisms, as well as human embryos, has become routine in science and medicine over recent decades.[10][11][12] The revival of adult human beings is not currently possible, partially due to the size of the tissues involved. It is currently possible to vitrify and revive small organisms with very little damage, but in larger organisms, various types of tissue damage are caused by the perfusion, cooldown, and the rewarming processes.[20]

Known: The detailed repair of an organism does not conflict with any known scientific principles.

Information theoretic death is the disruption of the structures which encode memory and personality within a brain to such an extent that the recovery or repair of the original person becomes theoretically impossible.[21] As long as a person has not suffered information theoretic death, there is no known scientific principle that would prevent the use of sufficiently advanced medical technology to repair or rejuvenate the person to an appropriate level of functionality. As of 2020, there are no peer-reviewed scientific papers which claim that cryonics cannot work. However, there are writings in other media which are skeptical about cryonics. In general, the scientifically minded writings against cryonics revival have tended to argue against its feasibility, or sometimes its desirability, but not its scientific possibility.[22][23] Some writings have incorrectly assumed that the purpose of cryonics was to copy the patient's mind into a digital form (also known as mind uploading), instead of the repair and revival of their biological body.[24]

Known: Medical repair technologies have historically tended to become more capable over time.

The ability of medical technology to repair human tissue has unambiguously increased and accelerated over historic timescales.[25][26] Examples of these trends can be seen in the medical milestone timelines for the last 500 years, 50 years, or decade. The size scale at which tissue repairs can be performed has also become smaller over time, with cellular and molecular scale tissue repairs only recently becoming possible. Examples of tissue repairs at these scales are therapeutic gene editing, stem cell technologies, organ 3-D printing, and cancer immunotherapies. The historic trends for medical technologies to become increasingly capable, at increasingly smaller scales, implies that future medical technologies could possibly or even likely be more capable of repairing damaged tissues than they are today. However, it is generally very difficult to accurately predict the capabilities or limits of future technologies, especially when trying to forecast more than a decade or so into the future.[27][28][29]

Unknown: How much of the human mind is preserved during cryopreservation? (How much damage occurs?)

It is not yet known how much of the neurological basis of the mind is preserved using current cryopreservation technologies. Cryonics cooldown and rewarming procedures do cause some amount of tissue damage. The amount of damage is estimated to be relatively small in some cases, and larger in other cases, depending on the circumstances and techniques that were used with each particular cryonics patient. There is reason to believe that with the best currently achievable vitrification procedures, and the best cryopreservation timelines, that the small-scale neurological structures of the brain are preserved very well.[14][30][11] At the other end of the spectrum, the amount of neurological tissue damage increases whenever a particular cryopreservation is significantly delayed, or when a "straight freezing" process is performed instead of a vitrification. One reason it is difficult to quantify how much of the mind is preserved using current cryonics procedures, is that the neurological basis of the human mind is not yet completely understood by science.[15] The current research into how human personality and memories are biologically encoded is still in its early stages. Hypothetically, if there is a partial loss of neurological information caused by tissue damage, then a cryonics patient may have partial loss of preexisting behaviors or memories after repair and revival.[31][17]

Unknown: How much tissue damage will be repairable by future medical technologies? (Are comprehensive repairs feasible?)

Predicting the capabilities of future technologies is inherently difficult.[29] Historically, medical repair technologies have become increasingly capable over time. Some scientists claim that medical technologies can be foreseen, such as nanotechnology, and detailed tissue regeneration, which may be able to repair the tissue damage that is caused by current cryopreservation technologies.[4] Other scientists are skeptical that sufficiently advanced medical technologies will ever exist.[23] In general, there is no way to predict for certain the capabilities and limits of future technologies, until the time that those technologies are developed.

Unknown: Will the cryonics organizations survive long enough for repair technologies to mature? (How long could that take?)

No one knows how long it could take before advanced molecular scale medical repair technologies are developed, or if they will be developed at all. If such technology does become possible, it could take decades or even centuries. It's unknown how long cryonics storage organizations can continue to survive, and can maintain their patients in liquid nitrogen. So far, the longest that any human has been cryopreserved is about 53 years, as of 2020. Within that timeframe, the two largest cryonics organizations (Alcor and the Cryonics Institute), have had a consistent record of maintaining their cryonics patients at liquid nitrogen temperatures.[32][6][7]

Past Revivals of Whole Organisms

Various living organisms have been successfully revived after freezing, either in the lab or in nature. Medical and laboratory revivals of whole organisms have included Human embryos, adult C. Elegans, and fly larvae.[10][11][12] Notably, it is not yet possible to revive humans who were cryopreserved after the embryonic stage. The process of cooling to cryogenic temperatures tends to create conditions for tissue and cellular damage, but while cryogenic temperatures are maintained, little to no damage occurs.

Human embryos are routinely cryopreserved in medicine for assisted human reproduction. Embryos are most commonly vitrified at the blastocyst stage, which is 3-days or 5-days after conception. Slow cooling techniques were first used to freeze viable embryos starting in 1984. The first birth from a cryopreserved embryo occurred in 1998. Since then, the cryopreservation of embryos has become increasingly common, due to improved embryonic survival rates and better clinical outcomes.[10] In 2017, a healthy baby girl, Emma Wren Gibson, was born after being cryopreserved as an embryo for 24 years.[33] That was a record for the longest time a human embryo had been cryopreserved before a revival and a live birth.

Memory Retention Experiments

In 2015, it was demonstrated for the first time that memories can be retained after the cryopreservation of a whole organism. Adult Caenorhabditis Elegans nematode worms were instilled with memories of specific chemical odors. They were then cryopreserved in liquid nitrogen, and revived. After revival, they were tested for the retention of the odor memories, and it was shown that the memories were still present.[11]

The Scientists' Open Letter on Cryonics

The Scientists' Open Letter on Cryonics is a collaborative document in support of cryonics. The signatories are largely PhD holding scientists, researchers, or professors. Together they encompass various fields relevant to cryonics, such as: Biology, Cryobiology, Neuroscience, Physical Science, Nanotechnology, Computing, Ethics, and Theology. A quote from this letter is below.

To whom it may concern,

Cryonics is a legitimate science-based endeavor that seeks to preserve human beings, especially the human brain, by the best technology available. Future technologies for resuscitation can be envisioned that involve molecular repair by nanomedicine, highly advanced computation, detailed control of cell growth, and tissue regeneration.

With a view toward these developments, there is a credible possibility that cryonics performed under the best conditions achievable today can preserve sufficient neurological information to permit eventual restoration of a person to full health.

The rights of people who choose cryonics are important, and should be respected.

(68 Signatories)

Standard Cryopreservation Procedures

A standard cryopreservation procedure[34][35] has six phases:

  1. Standby: As a dying patient’s condition becomes critical, transport personnel wait nearby on a 24-hour basis.
  2. Stabilization: The patient is placed in an ice water bath, and breathing and circulation are artificially restored with a heart-lung resuscitator. Protective medications are also administered, including free radical inhibitors, anticoagulants, and anesthetics.
  3. Transport: After stabilization, patients will be transported to their cryonics facility.
  4. Cryoprotective Perfusion: Major blood vessels are connected to a perfusion circuit by a surgeon. A preservation solution circulated through the patient at a temperature near 0°C.
  5. Final Cooldown: After cryoprotective perfusion, patients are cooled under computer control by fans circulating nitrogen gas at a temperature near -125°C.
  6. Storage: Patients are placed into vacuum-insulated dewars, for long term storage in liquid nitrogen at a temperature of -196°C.

These phases describe a standard cryopreservation protocol. However, the circumstances surrounding a person's death can differ from person to person, and therefore the standard protocol is sometimes modified depending on the circumstances surrounding a person's death. An example of modified protocol is a "Straight Freeze" procedure. A straight freeze is the freezing of a cryonics patient to liquid nitrogen temperatures without introducing cryoprotectants. This can be performed in cases where cryoprotective perfusion is no longer feasible. A straight freeze procedure is less desirable that the standard protocols, because a freezing without cryoprotectants causes small ice crystals to form in the body from the water in tissues. Those crystals cause significant damage to the cellular membranes in the brain, and in other tissues of the body.

During the first two phases (stabilization and transport), time is of the essence. Ideally, the stabilization phase will begin within seconds of the pronouncement of a person's clinical death. Clinical death refers to the cessation of heartbeat and respiration. The transport phase should also proceed as quickly as possible. In an idealized cryopreservation procedure the cold ischemia associated with the transport phase can be minimized or eliminated. This can be accomplished if, 1) The person relocates to the same city as their cryonics facility at some point before death occurs, or 2) A field cryoprotection procedure is performed.

The reason it is desirable to start the perfusion and final cooldown phases as quickly as possible after clinical death, is to better preserve the fine cellular structures in the brain. These neural structures are commonly thought to encode for the major aspects of a person's identity, such as memory and personality.

The Cost of Cryonics

Cryonics is typically paid for using life insurance. As of 2020, the cost of a cryopreservation procedure is $80,000 at Alcor, or $28,000 at the Cryonics Institute, or $18,000 at KrioRus. (These prices are not directly comparable, because the features of the cryonics plans are different at each organization, including the options for standby and stabilization services.) The majority of people do not pay for cryopreservation "out of pocket". They typically pay for cryonics using a life insurance policy, which tends to make cryonics services more affordable. For example, the cost of a suitable term life insurance policy for a healthy middle-aged adult might be a few hundred dollars per year. The full cryopreservation costs are not due until the time of death, which is why cryonics services can generally be paid with a life insurance policy.

It is common for cryonics clients to purchase a term or permanent life policy with a face value of $250,000. (This policy size is also commonly offered by insurance companies.) As of 2019, a policy of this amount is more than sufficient to pay for a standard cryonics plan from any known cryonics organization, with significant funds remaining for other desired beneficiaries.


1931 - 1962

Research in cryobiology begins, and the idea of cryonics is conceived.

  • 1931: Robert Ettinger (the "Father of Cryonics") conceived the cryonics idea after reading a story called The Jameson Satellite.
  • 1947: While in the hospital for battle wounds, Robert Ettinger discovered that research in cryogenics was being done by French biologist Jean Rostand.
  • 1949: Bull semen was cryopreserved for the first time.
  • 1962: Robert Ettinger published his cryonics idea in a nonfiction book called "The Prospect of Immortality".

1963 - 1974

Early cryonics organizations are formed, but they struggle to maintain their patients in liquid nitrogen. Only 3 out of the 22 people cryopreserved during this period remain preserved to this day.

  • 1963: Evan Cooper founded the world's first cryonics organization, the Life Extension Society, which was intended to promote the idea of cryonics.
  • 1965: A New York industrial designer named Karl Werner coined the word "cryonics".
  • 1965: Early cryonics storage organizations were created. These included the Cryonics Society of California and the Cryonics Society of New York."
  • 1967: Dr. James H. Bedford became the first man to enter cryonic suspension. Bedford remains frozen to this day at Alcor.
  • 1968: A TV repairman, Robert Nelson, oversaw the worst historic cryonics disaster (the "Chatsworth Disaster"). Nine people were frozen, and later thawed.

1975 - 1999

The first professional cryonics storage organizations are created, and slowly grow during these years. Financial and procedural policies are developed which enable long term, stable patient storage.

  • 1976: Alcor carries out the first human cryopreservation where cardiopulmonary support is initiated immediately after clinical death is pronounced.
  • 1979: The first cryopreservation of a companion animal was performed, which was Mike Darwin’s childhood dog “Mitzi”.
  • 1980: Leaf et al., carried out the first closed circuit perfusions with controlled and monitored increases in cryoprotectant concentration.
  • 1981: The first paper suggesting that nanotechnology could reverse freezing injury is published.
  • 1984: The first paper showing that large organs can be cryopreserved without structural damage from ice is published.
  • 1995: Darwin et al., document the first use of a premedication protocol to mitigate ischemia injury in a cryonics patient.
  • 1995: Alcor begins using a concentrated glycerol solution as their cryoprotective strategy.
  • 1997: Alcor forms the Patient Care Trust as an entirely separate entity to manage and protect the funding for cryonics patients.

2000 - 2009

Cryonics organizations begin to use vitrification solution to preserve their patients. Stabilization and Transport organizations are formed.

  • 2000: The application of vitrification to a relatively large tissue of medical interest, vascular grafts, is successful for the first time.
  • 2002: Suspended Animation, Inc was created to provide advanced Stabilization and Transport services to other cryonics organizations.
  • 2002: Alcor cryopreserved baseball star Ted Williams. Two of his children stated that Williams wanted to be cryopreserved, but a third child objected.
  • 2003: Carnegie Mellon University receives a $1.3 million grant from the U.S. government to study vitrification of tissue for medical applications.
  • 2004: The Cryonics Institute uses a cryoprotectant, CI-VM-1, for the first time.
  • 2006: KrioRus was created in Moscow, Russia. This was the first cryonics storage organization located outside the United States.

2010 - 2019

Cryonics organizations grow at a faster rate in comparison to previous years. The concept of cryonics becomes more widely known to the public.

  • 2011: CI shipped its vitrification solution (CI-VM-1) to the United Kingdom so European cryonics patients can be vitrified before transport to the USA.
  • 2011: Robert Ettinger (the "Father of Cryonics") was cryopreserved at the Cryonics Institute, at age 92.
  • 2015: The New York Times published "A Dying Young Woman's Hope in Cryonics and a Future" for Kim Suozzi. Public interest in cryonics surged.
  • 2017: Southern Cryonics secured approximately $1 MM(AUD) to build the first cryonics facility in Australia, with construction to begin in 2020.
  • 2018: Alcor received a five million dollar donation to be used for research which would benefit cryonics technology.

Cryonics Organizations

Cryonics Storage Organizations

Stabilization and Transport Companies

Information and Advocacy

  • LongeCity, Information and Advocacy for Cryonics and Life Extension.

New Organizations and Projects

  • Southern Cryonics, A Cryonics Storage Organization constructing a new cryonics storage facility, in New South Wales, Australia. They are projected to open in 2022.


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