The Journey of Oxygen and Carbon Dioxide in Our Bodies Have you ever wondered what happens when you breathe in and out? Let's take a fun journey to understand how oxygen and carbon dioxide travel through our bodies. Breathing In: Oxygen Enters When you take a big breath, the air around you rushes into your nose or mouth. This air is full of something vital called oxygen. Oxygen is our fuel in the air because our bodies need it to stay alive. Down to the Lungs Once the oxygen enters your nose or