Micrographs of sections from d30 fused organoids, showing ventral GFP+ cells in the dorsal area. The migrating GFP+ cells were counted starting from 100 µm far from the ventral/dorsal border. Quantification of ventrally-derived GFP+ cells in dorsal/thickness of the counted area (µm3). The counted area was always 100 µm far from the border between ventral and dorsal area as indicated in Fig.EV5D. Every dot represents a different hCOs and different areas were counted for each hCO. Nuclei (blue) are stained with DAPI. 