In the field of assisted reproductive technology, vitrification is becoming an increasingly popular method of cryopreserving cells, tissues and even entire organs. The possibility that water might be vitrified was first proposed by Brayley in the mid 1800s, but the idea of cryopreservation by vitrification was apparently not introduced until Stiles observed, that protoplasm is likely, at very high cooling rates, to form "a finely crystalline or even amorphous mass" that "in thawing, might be expected to give again the original system without change". Vitrification does not inherently rely upon very high rates of cooling because ice nucleation and growth rates go down as solute concentration goes up. Vitrification can be seen as the means by which an aqueous solution remains within the bounds of thermodynamic law. The negative effects of vitrification solutions (VSs) can arise, not only from true biochemical toxicity but also from osmotic effects.