Some fungi are wasteful, while others recycle—and this can determine how much carbon is stored in a forest. Researchers at Lund University have now revealed how fungi manage their mycelium, the network that builds the structure of fungus. Using microfluidic chips—units that handle and analyze extremely small volumes of fluid through microscopic channels—the researchers could show that the availability of nutrients among fungi affects how much of the mycelium is recycled. The results could provide new insights into the carbon cycle and climate.