The Earth is made up of four interacting spheres: the atmosphere, biosphere, hydrosphere, and lithosphere. The atmosphere contains gases, regulates temperature, and facilitates heat transfer. The biosphere encompasses living things and their habitats. The hydrosphere is composed of the planet's water. The lithosphere constitutes Earth's solid and rocky materials. These spheres constantly influence one another through exchanges of matter and energy, such as in the water and carbon cycles. Changes in one sphere can trigger effects in the others through complex interactions that exemplify Earth's interconnected systems.