photosynthesis

Photosynthesis is how plants, algae, and some bacteria make their own food using sunlight. They take in water from the soil and carbon dioxide from the air, and use the energy in light to turn them into sugar — the fuel that keeps them alive and growing.

There's a wonderful bonus for the rest of us: as plants do this, they release oxygen as a leftover. Almost every breath you take is oxygen that some leaf, blade of grass, or speck of ocean algae quietly handed back to the air.

This one process is the foundation of nearly every food chain. When an animal eats a plant — or eats another animal that ate a plant — it's really living off energy that started as sunlight, captured and stored by photosynthesis.