Why is soil known as the habitat of many living organisms?

Soil is made up of particles of sand, silt, and clay, and it's full of nooks and crannies for things to live in. Plant roots penetrate the soil, and the Rhizosphere, the area within 1-2 mm of plant roots, is among the most biodiverse environments on the planet.

This is because plants pump a steady stream of nutrients--sugars, starches, and sloughed-off dead cells--into the soil to recruit microbial allies. Roots are completely encrusted with bacteria, fungi, and microarthropods feeding at the trough. Root-eating nematodes and plant pathogens have to fight their way through the crowd and Dodge predators to attack the plant.