Carbon Dioxide ( CO2) is one of the many gases that make up our atmosphere and composed of one carbon atom and two oxygen atoms bonded by double bonds. It is a byproduct of cellular respiration, so we interact with this molecule every time we breathe. During this process, glucose and oxygen react to form ATP, CO2, and water. In addition, CO2 is also present in a complementary process called photosynthesis that converts carbon dioxide and water into oxygen and glucose. Carbon dioxide molecules are 0.33nm in diameter and one of the smallest molecules. It is a greenhouse gas and traps heat in our atmosphere keeping the earth’s temperatures above inhabitable levels. Although CO2 can be harmful in some levels we also can’t live without it since it is essential to respiration and the atmosphere. All in all, CO2 is ever present around us and both necessary and harmful.