Segmentation of different PE clusters. 3D reconstruction of an epi:GFP 60 hpf zebrafish embryo. epi:GFP were immunostained for GFP in green, myosin heavy chain (MHC) in red and nuclei were counterstained with DAPI (blue). The ventral pericardium was digitally removed to allow a top view on the DP. avcPE and vpPE clusters were segmented (yellow and white colors, respectively). From second 10 onwards, transversal optical sections through the heart are shown to highlight the morphology of DP vs PE cells. at, atrium; avc, atrio-ventricular canal; DP, dorsal pericardium; PE, proepicardium; v, ventricle; vp, venous pole. Scale bar: 50 μm. Shown is a representative movie from ≥ 3 biological and ≥ 2 technical replicates.