Left: Time-lapse scanning laser confocal microscope video showing a calcium wave propagating through a root. In the root, these waves move through the cortical and endodermal cell layers at speeds of up to 400 µm/s, i.e., traversing several cells per second. This Ca2+ wave system correlates with the triggering of molecular responses in distant parts of the plant upon perception of localized (salt) stress. Such propagating Ca2+ waves provide a new mechanism for the rapid integration of activities throughout the plant body (Choi et al., 2014).