Dig into soil and you’ll find rock dust but also thousands of living species. ChristinLola/iStock/Getty Images Plus March 25, 2024 What is dirt? There’s a whole wriggling world alive in the ground beneath our feet, as a soil scientist explains Brian Darby, University of North Dakota Rock dust is only part of the story of soil. Living creatures, many of them too tiny to see, keep that soil healthy for growing everything from food to forests.