 We're studying Earth system science, which is a great big planetary system. It's composed in several different spheres, the biosphere being the one that I care about a lot as a biologist, but we also have the atmosphere, the air, which is mostly nitrogen and oxygen made by plants with a little bit of CO2 that keeps us warm or too warm. There's the lithosphere and the hydrosphere, which is the water cycle, which is the oceans and the rivers and the lakes and the clouds. And so we always have this cycling, especially how water moves from the atmosphere into the land and then back into the ocean and the hydrosphere and some of it freezes. And when those frozen glaciers grind up rocks, we're affecting the lithosphere, and when we dig deep into the earth to pull up fossil fuels, we're digging into the lithosphere, which is old fossil plants from hundreds of millions of years ago. All of these spheres are connected in our Earth system, and you can't as a biologist only look at one of them. We need to understand how climate change, which is warming the atmosphere, affects how plants grow, which feeds back on the atmosphere due to the fossil fuels that we extract from the lithosphere, which affects ice melt and sea level rise of the hydrosphere. So it's all connected and you've got the right topic here with Earth System Science.