Frogs have been hopping the planet for more than 350 million years. They’ve evolved into some of the most wondrous, diverse and beloved animals on earth. Suddenly, they’re slipping away. We’ve already lost one-third of our amphibians and more are disappearing each day. Some say it’s the greatest extinction since the dinosaurs. It’s a global crisis, NATURE follows as scientists are mobilized around the world to stem the tide — before the next frog crosses the thin green line.