Air is the mixture of gases which forms the Earth's atmosphere and which we breathe. Air is a mixture of nitrogen, oxygen, and minute amounts of other gases that surrounds the Earth and forms its atmosphere. Air is consistently present around us. A cool breeze is an example of Air. People need to breathe, and so do lots of other animals—and plants! Almost all living things breathe in and breathe out this Air. Air is essential for living things. Nitrogen and Carbon dioxide are also other gases that are vital for plants and their growth.