Three-dimensional morphology of Rathke’s pouch. (a) Rathke’s pouch at E11.5 in a wild-type mouse in coronal section, visualized using synchrotron X-ray microtomography after iodine staining. The oral ectoderm is still connected to the pouch (red arrow). (b) Three-dimensional reconstruction of the same sample. Anterior aspect clipped in the coronal plane. The diencephalon (blue) invaginates (black arrow) towards the pouch (yellow), which is still in continuity with the oral ectoderm (red arrow). (c) Posterior view of the forming pituitary at the same stage. The diencephalon evagination (black arrow) fits into a heart-shaped Rathke’s pouch (yellow) still connected to the oral ectoderm (red).