a, Confocal image of organoid stained for F-actin, DAPI and HLA-G with a merged image. A few isolated cells stain for HLA-G (arrowheads) at the periphery of the organoid. Scale bar, 50 μm. Representative images from n = 3. b, Phase-contrast images from time-lapse videos of trophoblast organoids grown for 16 h in TOM when EVT differentiation does not occur (top) and no invasive cells are visible. An organoid (middle) and a placental villous explant (bottom) exposed to EVTM are shown for comparison. Arrows indicate cells migrating, and arrowheads denote the visible tracks made as the cells invade through the Matrigel. For time-lapse videos of these cultures, see Supplementary Videos 1, 4 and 5. Scale bars, 200 μm.