August 09, 2026 | Source: BBC Science Focus | by Michael Day

Right now, beneath almost every patch of soil on Earth, one of the planet’s strangest living structures is spreading. It’s a fungus, though nothing like the mushrooms on your dinner plate. Instead, it grows as microscopic threads, finer than cotton, weaving through the soil and into the roots of most plants.

There are several types of these root-dwelling fungi. The most widespread – and the focus of a major new study – are arbuscular mycorrhizal, or AM, fungi. They’ve been around for hundreds of millions of years, long before the first trees.

Scientists have known for more than a century that they help keep ecosystems alive by ferrying nutrients and water to plants. Yet one surprisingly basic question has remained unanswered until now: just how much of this hidden network is buried underground?