Trees use carbon dioxide during the process of photosynthesis. Here's how it works:

* Sunlight: Trees absorb sunlight through their leaves.

* Water: Trees absorb water from the soil through their roots.

* Carbon dioxide: Trees take in carbon dioxide from the air through tiny pores on their leaves called stomata.

Inside the leaves, the tree combines the sunlight, water, and carbon dioxide in a complex chemical reaction. This reaction produces:

* Glucose (sugar): This is the tree's food source.

* Oxygen: This is released back into the atmosphere.

So, in essence, trees use carbon dioxide to build their own food and grow. This process also helps remove carbon dioxide from the atmosphere, making trees important for mitigating climate change.