This story initially appeared in Hakai and is a part of the Climate Desk collaboration.

Arah Narida leans over a microscope to gaze right into a plastic petri dish containing a hood coral. The animal—a pebbled blue-white disk roughly half the scale of a pencil eraser—is a marvel. Just three weeks in the past, the coral was smaller than a grain of rice. It was additionally frozen stable. That is, till Narida, a graduate pupil at National Sun Yat-sen University in Taiwan, thawed it with the zap of a laser. Now, simply beneath the coral’s tentacles, she spies a slight divot within the skeleton the place a second coral is starting to bud. That small cavity is proof that her hood coral is reaching maturity, a feat no different scientist has ever managed with a beforehand frozen larva. Narida smiles and snaps an image.

“It’s like if you see Captain America buried in snow and, after so many years, he’s alive,” she says. “It’s so cool!”

For almost 20 years, scientists have been cryopreserving corals—freezing them at temperatures as little as -196 Celsius for long-term storage. The aim has been to someday plant corals grown from cryopreserved samples on reefs tormented by bleaching and acidification. Yet, progress has been agonizingly sluggish. When Narida and her colleagues published a study earlier this yr detailing how they efficiently grew grownup corals from cryopreserved larvae, it was a milestone for the sector.

Coral cryopreservation is troublesome partially as a result of freezing and thawing wreak havoc on cells. As scientists decrease the temperature, the water within the coral’s cells turns to ice, leaving them dehydrated and deflated. Reheating is simply as delicate: If the coral is warmed too slowly, melting ice can refreeze and tear via the cells’ outer membranes. The result’s a soggy mess, because the cells’ innards ooze out via jagged holes—image a frozen strawberry turning into limp and shriveled because it thaws.

Through trial and error, although, cryobiologists have developed the methods that helped Narida develop her hood coral to maturity. To forestall ice harm, Narida says, she washes the animals in antifreeze first. Antifreeze could be poisonous, nevertheless it additionally seeps into the larvae’s cells and pushes out the water, serving to the coral survive the following step: being dunked in liquid nitrogen.