This is a dorsal section through a zebrafish embryo during gastrulation showing neurectoderm tissue (cell nuclei in cyan and cell membrane in magenta) and underlying mesendodermal tissue (green cells) ...

Only two weeks after fertilization, the first sign of the formation of the 3 axes of the human body (head/tail, ventral/dorsal, and right/left) begins to appear. At this stage, known as gastrulation, ...

Prior to gastrulation the mouse embryo exists as a symmetrical cylinder consisting of three tissue layers. Positioning of the future anterior-posterior axis of the embryo occurs through coordinated ...