Breathe in. You just inhaled air that was full of oxygen. Our bodies need this oxygen we just breathed in to survive.
Now breathe out. You just blew out air that was full of a gas called carbon dioxide, or CO2. CO2 is made in our bodies when our bodies turn the food we eat into energy to keep us going. 
But wait. If everyone in the entire world is taking in oxygen and putting back CO2, how come we never run out of oxygen to breathe?
It's simple. The earth has built-in solar powered air filters. 
No, not that kind of air filters.
These kinds of air filters. 
Plant leaves have 2 important features that help clean the earth's air. 
First, plant leaves have tiny holes called stoma. A plant uses the stoma in its leaves to pull in CO2 from the air. 
Plants leaves also have microscopic parts called chloroplasts that make a special chemical called chlorophyll.
The chlorophyll in the leaves absorbs sunlight to make energy.
And just like we get rid of co2 when we turn food into energy, plants get rid of oxygen as they make their own energy.
So, you can keep on breathing easy now that you know how plants do the job of cleaning the air we breathe.
