The ability to perform hygroscopic movements has evolved in many plant lineages and relates to a multitude of different functions such as seed burial, flower protection or regulation of diaspore release. In a recent Editor’s Choice article published in AoB PLANTS, Gallenmüller et al. provide an analysis of spore liberation in mosses in response to humidity conditions. The study presents, for the first time, temporally and spatially well-resolved kinematic analyses of the complex hygroscopic movements performed by the peristome teeth inserted at the mouth of the spore capsule and gives insights into their sophisticated functional morphology and anatomy. The authors explain these movements by relating gradients in the composition of the peristome teeth to differences in swelling capacity and velocity between the tip and the base of the teeth and also between different teeth layers.