Most animals run from winter. They fly south, dig deep, or hide in caves. But in the frozen forests of Alaska and Canada, the wood frog does something almost impossible: it lets winter kill it. Sort of.

When temperatures drop below freezing, ice crystals start forming inside the frog's body. Its heart slows. Then stops. Its lungs stop. No breathing. No heartbeat. Up to 70% of the water in its body turns to solid ice. By every normal measure, the frog is dead.

But here's the trick: the frog floods its cells with glucose—basically, sugar—right before it freezes. Imagine wrapping each cell in a protective sugar blanket. The glucose keeps the insides of cells from freezing solid, even when ice forms everywhere around them.

Ice is dangerous because when water freezes, it expands. Ice crystals can puncture cell walls like tiny knives. But the wood frog lets ice form only outside its cells, in the safer spaces between them, while the glucose keeps the cell interiors liquid and squishy.

The frog also moves most of its water out toward its skin and organs, away from the most delicate inner parts. Its liver makes extra glucose and pumps it through the body like an emergency antifreeze delivery system. Everything happens in just a few hours.

And then the frog waits. Frozen. For weeks, sometimes months. No heartbeat. No brain activity. A living thing that has paused itself, like a video on pause, trusting that spring will come.

When temperatures rise, the magic reverses. Ice melts from the outside in. The heart twitches—once, twice—then starts beating steadily. Lungs inflate. Within a day, the frog blinks, stretches its legs, and hops away to find breakfast.

No other animal with a backbone can do this. The wood frog survives by turning winter's deadliest weapon—ice—into a waiting room. It doesn't fight the freeze. It just knows how to come back.