Imagine living in an old house for years and finally getting access to a locked basement?"only to discover a magical workshop where everything in the world is made. That's a bit what it was like recently for geologists to finally get a good glimpse of the mantle, that vast middle layer of Earth that begins some 20 miles beneath the surface of the continents. Last month, an international research team published their analysis of the longest core sample of the mantle to date in Science. The mantle, which constitutes 80 percent of Earth's volume, is fundamental to the character of our planet: All crustal rocks?"and everything derived from them, including our bones?"can trace their origins to magmas that melted out of it. Our atmosphere is continuously regenerated by mantle gasses exhaled by volcanoes, then processed by algae and plants. The mantle's movements also dictate how fast tectonic plates travel at the surface, shifting continents, building mountains, and unleashing ea