A handful of healthy soil is one of the busiest places on Earth. A single gram can hold billions of bacteria, along with fungi, tiny animals and the roots that feed them, all working in the dark.

Fungi spread thread-like networks through the ground, trading water and minerals with plant roots in return for sugars. Earthworms pull dead leaves down from the surface and leave rich, crumbly casts behind. Bacteria break down what is left, releasing nutrients that plants can use again.

Together they build soil’s structure: the small clumps and spaces that let water soak in and air reach the roots. Soil like this holds water through dry spells and drains after heavy rain.

It forms slowly, a few centimetres over centuries, and can be lost in a single season of erosion. That makes the ground beneath our feet one of the most valuable things we have.