139 Essays on Infinite Lifespans   Brian Wowk New  breakthroughs  in  reducing  the  toxicity  of  vitrifica- tion  solutions  [20],  and  in  adding  synthetic  ice  blocking molecules   [21;22]   continue   to   push   the   field   forward. In  2004,  successful  transplantation  of  rabbit  kidneys  after cooling  to  a  temperature  of  -45°C  (-49°F)  was  reported. [23] These kidneys were prevented from freezing by replac- ing more than half of the water inside them with vitrification chemicals. Amazingly, organs can survive this extreme treat- ment if the chemicals are introduced and removed quickly at low temperature. Reversible vitrification of major organs is a reasonable pros- pect within this decade. What about vitrification of whole animals? This is a much more difficult problem. Some organs, such as the kidney and brain, are privileged organs for vit- rification because of their high blood flow rate. This allows vitrification chemicals to enter and leave them quickly before there are toxic effects. Most other tissues would not survive the long chemical exposure time required to absorb a suffi- cient concentration to prevent freezing. It is useful to distinguish between reversible vitrification and morphological vitrification. Reversible vitrification is vitrifi- cation in which tissue recovers from the vitrification process in a viable state. Morphological vitrification is vitrification in which tissue is preserved without freezing, with good structural preservation, but in which key enzymes or other biomolecules are  damaged  by  the  vitrification  chemicals.  Morphological vitrification of a kidney was photographically demonstrated in Fahy’s original vitrification paper [17], but 20 years later reversible kidney vitrification is still being pursued. Given this background, what are the prospects of reversibly vitrifying a whole human being? It is theoretically possible, but the prospects are still distant. Morphological vitrification of most organs and tissues in the body may now be possible, but  moving  from  morphological  vitrification  to  reversible