Invisible and everywhere, air is a very important element. The air is made up of many different elements, each important to our survival. Without oxygen, our bodies couldn't engage in the complex chemical reaction known as aerobic respiration. Through this book's look at the air, readers learn about the invisible force all around them--and why living things need it. From the air they breathe, to the wind that blows strong enough to knock down trees, there's a lot to discover about the air!