It is tempting to treat the cryoprotectant solution as a fixed thing, a single clever recipe that makes vitrification possible. It is nothing of the sort. The medical antifreeze in use today is the latest survivor of roughly forty years of iteration, a lineage of solutions in which each generation existed to fix a specific, named flaw in the one before it. Reading that history is the best way to understand why the current solutions look the way they do, and why nobody claims they are the last word.
The thread running through the whole story is a single tension. To vitrify, you need a high enough concentration of cryoprotectant to stop ice from forming. But cryoprotectants are toxic, and the more you use, the more you poison the tissue you are trying to save. Every generation in this lineage is one more attempt to get the ice-blocking benefit without paying the full toxicity bill.
1984: Fahy proposes vitrification
The conceptual leap came from cryobiologist Greg Fahy, who in 1984 proposed using vitrification, rather than controlled freezing, for cryopreservation. The idea was to abandon the losing battle against ice crystals entirely. Instead of trying to freeze tissue gently enough that the crystals stayed small, you would load it with enough cryoprotectant and cool it fast enough that water never crystallized at all, setting instead into a glass. This is the distinction the field still turns on, explored in the difference between freezing and vitrification. The proposal reframed the problem from "how do we make ice harmless" to "how do we avoid ice while surviving the chemistry that lets us", and the chemistry has been the work ever since.
The generations, each fixing the last one's flaw
What followed was an evolution you can read like a changelog, each version patching a defect.
- Early single-agent mixes. The first attempts leaned heavily on a single cryoprotectant. They could vitrify small samples but were too toxic at the concentrations needed for larger tissue.
- DMSO with amides and propylene glycol. Combining agents let each do part of the job at a lower, less toxic dose. Solutions built on DMSO together with amides such as acetamide or formamide, plus propylene glycol, marked a real step forward. Formulations in this family, including ones known as VS41A and VS55, could vitrify meaningful volumes of tissue.
- Ethylene glycol in place of propylene glycol. Propylene glycol carried its own toxicity and chilling problems. Swapping in ethylene glycol reduced them while keeping the ice-blocking power.
- Added polymers. Large polymer molecules were introduced to help stabilize the glass and suppress ice without piling on more of the small toxic agents.
- Ice-blocking molecules. Specialized molecules that interfere directly with ice nucleation let the same vitrification be achieved at lower total concentrations, again buying ice resistance without extra toxicity.
- Raised tonicity of the non-penetrating components. A subtle but important fix. Increasing the tonicity of the parts of the solution that do not enter cells helped counter chilling injury, a form of cold-induced damage separate from ice, improving how tissue tolerated the deep cold.
None of these was a revolution on its own. Together they are why a modern cryoprotectant can vitrify large tissue at concentrations that earlier solutions could not have survived.
The current human-use solutions: VM1 and M22
That lineage converges on the two solutions used for human cryopreservation today. VM1 is used by Tomorrow.bio and the Cryonics Institute; M22 is used by Alcor. Both are direct descendants of Fahy's line, incorporating the hard-won lessons above: multi-agent blends to spread the toxicity load, ice-blocking molecules, and careful tuning of the non-penetrating components. They are not interchangeable, and the differences between providers' solutions are part of why choosing a provider is a real decision rather than a formality.
One tool deserves a mention because it shows how the field grew up. Developing these solutions used to mean testing toxicity by trial and error, an expensive and slow way to fail. The introduction of a toxicity-prediction metric, often written qv*, let researchers estimate the toxicity of a candidate solution in advance and steer toward less harmful formulations before ever touching tissue. Turning toxicity from a surprise into a number you can optimize is exactly the kind of maturation that moves a field forward, the same impulse behind advancing the field more broadly.
Proof it works beyond cryonics
It would be fair to ask whether this whole lineage actually preserves anything, or just sounds rigorous. The reassuring answer is that vitrification has been demonstrated on real tissue outside the cryonics context. Vitrified and rewarmed samples of heart valves, cornea, blood vessels, and brain slices have retained structure and, in cases, function. These are not whole humans, and honesty requires saying that scaling from a slice to a body remains hard, a point made plainly in the technical challenges for high-quality preservation. But they establish that the core move, replace water with antifreeze and set into a glass, genuinely keeps biological structure intact.
The first person, and what the history implies
The human milestone came in 2000, when FM-2030, the futurist and transhumanist thinker, became the first person to be vitrified rather than straight-frozen. That moment sits inside a longer arc told in a brief history of cryonics, and it marks the point where the chemistry above stopped being a laboratory exercise and started being applied to people.
The deeper lesson of this history is the one worth carrying away. The solutions improved generation by generation, each one fixing a concrete flaw, which means todays solutions are not a finished artifact handed down from on high. They are the current best version of a recipe that has been getting better for forty years, and there is no reason to think VM1 and M22 are where it stops.
The medical antifreeze that vitrifies a person today is not an invention but a lineage, each generation patching the toxicity or the ice that defeated the last.
That is both a humbling and an encouraging place to stand. Humbling, because it means current solutions are imperfect by construction. Encouraging, because a recipe that has improved steadily for four decades is exactly the kind of thing that keeps improving, and every improvement raises the odds for the people preserved with it.