Two oxygen atoms make O₂. It’s the oxygen we breathe in. We breathe out carbon dioxide. Trees take in carbon dioxide and turn it into the oxygen we breathe. Oxygen is important to our world because it keeps things alive. The oxygen goes into our bloodstream. Oxygen has no taste, color, or smell. Oxygen makes a fire burn a lot faster. In a water treatment plant, there are little tiny organisms that you can’t see without a microscope and oxygen helps make them hungry so that they help clean the water.