An ambitious goal in biology is to understand the behaviour of cells during development by imaging—in vivo and with subcellular resolution—changes of the embryonic structure. Important morphogenetic movements occur throughout embryogenesis, but in particular during gastrulation when a series of dramatic, coordinated cell movements drives the reorganization of a simple ball or sheet of cells into a complex multi-layered organism1. In Xenopus laevis, the South African clawed frog and also in zebrafish, cell and tissue movements have been studied in explants2,3, in fixed embryos4, in vivo using fluorescence microscopy5,6 or microscopic magnetic resonance imaging7. None of these methods allows cell behaviours to be observed with micrometre-scale resolution throughout the optically opaque, living embryo over developmental time. Here we use non-invasive in vivo, time-lapse X-ray microtomography, based on single-distance phase contrast and combined with motion analysis, to examine the course of embryonic development. We demonstrate that this powerful four-dimensional imaging technique provides high-resolution views of gastrulation processes in wild-type X. laevis embryos, including vegetal endoderm rotation, archenteron formation, changes in the volumes of cavities within the porous interstitial tissue between archenteron and blastocoel, migration/confrontation of mesendoderm and closure of the blastopore. Differential flow analysis separates collective from relative cell motion to assign propulsion mechanisms. Moreover, digitally determined volume balances confirm that early archenteron inflation occurs through the uptake of external water. A transient ectodermal ridge, formed in association with the confrontation of ventral and head mesendoderm on the blastocoel roof, is identified. When combined with perturbation experiments to investigate molecular and biomechanical underpinnings of morphogenesis, our technique should help to advance our understanding of the fundamentals of development.

We present results of damage studies conducted at the Free Electron LASer in Hamburg ͑FLASH͒ facility with 13.5 nm ͑91.8 eV͒ and 7 nm ͑177.1 eV͒ radiations. The laser beam was focused on a sample of 890-nm-thick amorphous carbon coated on a silicon wafer mimicking a x-ray mirror. The fluence threshold for graphitization was determined for different grazing angles above and below the critical angle. The observed angular dependence of F th is explained by the variation in absorption depth and reflectivity. Moreover, the absorbed local dose needed for the phase transition leading to graphitization is shown to vary with the radiation wavelength.

Synchrotron radiation laminography with X-ray diffraction contrast enables three-dimensional imaging of dislocations in monocrystalline wafers. We outline the principle of the technique, the required experimental conditions, and the reconstruction procedure. The feasibility and the potential of the method are demonstrated by three-dimensional imaging of dislocation loops in an indent-damaged and annealed silicon wafer.