[Music] Earth is kind of like a puzzle. And I don't mean a puzzle, like, where did my brother put my hairbrush? Or what exactly is in the tacos they serve on Taco Tuesday? I mean that our planet is made up of four very different parts that all work together to make Earth the lovely place that we know it to be. We call these parts "spheres," and between them, they contain all the stuff on our planet. Everything from the fish in the ocean to the air we breathe. Earth has four spheres: the geosphere, the biosphere, the hydrosphere, and the atmosphere. So what exactly are the spheres? And what's in them? Let's take a look at two: the geosphere and the biosphere. Up first is the geosphere. "Geo" comes from the Greek word for "ground." You may have heard this before in words like "geology" or "geography." It basically means having to do with the Earth. And in a way, the geosphere is kind of like the skeleton of our planet. All of the other spheres are built on top of it. It's made up of all the rocks and minerals on Earth, from the biggest boulders to the tiniest grains of sand. And all of the landforms that those rocks and minerals make up are part of the geosphere, too. I'm talking volcanoes, canyons, beaches, mountains, you name it! If it's made out of solid Earth, it's part of the geosphere. Now, it's important to remember that the geosphere includes only non-living stuff. Living things do need to eat, though. And all living things are part of another one of Earth's spheres: the biosphere. "Bio" is Greek for "life," and like "geo," you've probably heard it before in words like "biology," the study of life. The biosphere is made up of many different biomes. Biomes are regions that have similar kinds of plants, animals, and other living things that have adapted to live in that particular region's terrain and climate. Deserts and forests are types of biomes. So are rainforests, grasslands, and wetlands. All of these biomes and many more make up the biosphere. 'Kay, now that we know what's in these two spheres, let's put them together and try to figure out what belongs to which sphere. Imagine a lovely forest meadow: a bird perched on a rock, chirping away; a deer standing in the tall grass; a mountain standing tall in the background, in a stream flowing through the clearing. Ah, I can almost smell it! Almost everything in this scene is part of either the geosphere or the biosphere. Let's see if we can figure out which parts go into which sphere. Let's start with the geosphere. We know that there's nothing alive in the geosphere, so we can rule out all the plants and animals. Water is also part of a different sphere, but we'll talk about that later. When we take away the living things, we're left with all the solid Earth parts of the scene. The rock the bird was standing on, the soil the grass was growing out of, the mountain in the distance, and the bed the stream water flowed through. So what we're left with is the geosphere: rocks, soils, and landforms. Got it? Now, let's think about the biosphere. Unlike the geosphere, everything in the biosphere is alive. So the rocks, the mountain, and the stream, they don't count. Now we're just left with the living things: the grass, the birds, the deer. Voila! You found the biosphere! So now you know two of Earth's four spheres: the biosphere and the geosphere. While they're different puzzle pieces of Earth, they work together to help make our planet what it is. 'Kay, now I gotta go find where my brother put my hairbrush.