Details of embryos 35 min to 40 min after the initiation of inversion (late-inversion stage). cLSM and SEM images of intact embryos and an LM image of a physical cross-section. (A, F) Midsagittal cLSM optical cross-section of an embryo showing the localization of F-actin (red) using phalloidin-TRITC (see Figure 5D1 for an overview). (B, G) Midsagittal cLSM optical cross-section of an embryo showing the localization of both F-actin (red) and nuclei (blue) with a phalloidin-TRITC/DAPI overlay (see Figure 5D3 for an overview). (C) LM image of a physical midsagittal cross-section (see Figure 4G for an overview). (D, E) cLSM optical cross-sections perpendicular to the midsagittal cross-sections showing the localization of (D) F-actin (red) alone or (E) both F-actin (red) and the nuclei (blue). (H) SEM view of a mostly inverted embryo (see Figures 3G and 4G for an overview); a broken line indicates the edge of the opening, and a rectangle highlights an image detail shown in (I); and arrowheads point to a reproductive cell (gonidium). (I) Detailed SEM view of the cell monolayer from inside the spheroid (see H for an overview); arrowheads point to some of the numerous CBs. (J) Detailed SEM view of the cell monolayer from outside the spheroid (see Figures 3G and 4G for an overview); arrowheads point to some of the outgrowing flagella. (A, B, D, E) Broken lines refer to views that are perpendicular to the image plane. Scale bars: (A, B, C, D, E, F, G) 10 μm; (H) 5 μm; (I, J) 3 μm. CB: cytoplasmic bridge; cLSM: confocal laser scanning microscopy; DAPI: 4',6-diamidino-2-phenylindole dihydrochloride; F-actin: filamentous actin; LM: light microscopy; SEM: scanning electron microscopy; TRITC: tetramethylrhodamine B isothiocyanate.