Photosynthesis (photo-sin-thu-sis) is a process that plants use to make themselves food, and make us oxygen. It is a complicated name for a complicated process, so I’ll try to break it down for you. Basically, the sun hits the plant or tree, and the plant uses some of that energy to turn water and carbon dioxide into a thing that it can “eat” and grow with. What’s left over is a bunch of oxygen! God was a great engineer when he made the earth, because with all of the plants in the world converting yucky carbon-dioxide (what comes our of our mouth when we breath out) into wonderful, pure, oxygen, we never run out of air to breath!