Researchers discovered that a common wood-decaying fungus called Fomitopsis pinicola can break down wood even when there is no oxygen present, which happens in the interior of fallen trees. Instead of using the chemical process it normally uses in oxygen-rich conditions, the fungus switches to releasing powerful digestive enzymes that break down plant fibers. This finding explains how wood continues to decompose deep inside tree trunks and could inspire new industrial processes for breaking down plant material without oxygen.