Here's how it works:

* Mammals breathe in oxygen and breathe out carbon dioxide. This is a byproduct of respiration, the process of using oxygen to break down food for energy.

* Plants take in carbon dioxide through tiny openings called stomata on their leaves. They use this CO2, along with water and sunlight, to produce sugars for energy and growth through photosynthesis.

This exchange of gases is a crucial part of the carbon cycle, a natural process that keeps the Earth's atmosphere balanced.