This is a 3µm transverse slice (#15) of the rat E10 egg cylinder. The slice cuts the anterior part of the embryo on the left and is still above the level of the embryo on the right. Surrounding uterine tissue is not in the picture. All of the structures seen in slices #1, 2, and 3 are in this slice as well as two new structures.
The neuroepithelium of the brain is represented by two mounds of cells (the neural folds) on either side of a neural groove in the midline (a line that divides the body into right and left halves). Although it is not labeled, the prechordal plate is a layer of cells just beneath the brain neural groove. You can see a definite separation between it and the overlying neural ectoderm when you zoom to the highest resolution view of that area.