We think of trees as having no movement at all — but that’s not true. In addition to growing upward toward the sky and extending their roots into the ground, trees move water through their bodies in daily cycles. They show subtle expansion and contraction driven by water transport — a hydraulic rhythm in each trunk, almost like a forest breathing. As transpiration pulls water upward during the day, trunks contract slightly; at night, when internal water pressure is restored, they expand again. This subtle pulse, known as diurnal stem diameter fluctuation, is not true breathing, of course — but in a quiet way, the forest does have a heartbeat.

• Domain: Eukaryota > Kingdom: Plantae > Phylum: Tracheophyta (vascular plants)