Example of a 3D reconstruction of an embryonic heart at E9.5 by HREM. The first sequence shows a 3D projection, rotating rightward, of an E9.5 embryo imaged by HREM. The second sequence shows serial transverse sections of the thoracic region. The final sequence displays a 3D reconstruction of the embryonic heart shape, after image segmentation. It is first presented within the image of the thoracic region, and then isolated, using the notochord as an axial reference. AVC, atrioventricular canal. x/y resolution,1.45 μm; z resolution,1.56 μm.