The dry matter in a plant is made up of 90% carbon, hydrogen and oxygen. The majority content, which is carbon, is taken into the plant through carbon dioxide (CO2) available from the air. The average air that we inhale contains 0.003-0.004% of carbon dioxide. Carbon dioxide is an odorless, non-flammable, colorless gas. It is believed that the prehistoric plants that developed eons ago had environmental conditions with very high levels of carbon dioxide in it. In today’s plants, due to their evolution, these more modern incarnations have maintained their capacity to harness more CO2 than the current environment now has.