(k) Graphic representation of a neuroepithelial tissue with nuclei colour-coded to indicate clusters of high or low HES5 expression. The tissue is illustrated at three different time points to depict how clusters of cells can dynamically switch from high to low or low to high while the periodic spatial pattern is maintained. In the example time traces (corresponding to the three grey and one red highlighted nuclei), synchronised ultradian oscillations are shown as being overlayed on the slow-varying higher-amplitude switching dynamics. 