What Is Soil Made Of?

Soil is much more than 'just dirt!' It is a mixture of many things. Tiny broken-up rocks and minerals form the base. Dead leaves, bark, and plant parts break down and mix in. Water fills tiny spaces between the pieces. Air fills spaces too — yes, there is air underground! And billions of tiny living things like bacteria, fungi, and worms live in soil. One tablespoon of healthy soil has more living things in it than there are people on Earth!