Adjacent horizontal sections of forebrain including thalamus (T) and brainstem of a 12 wpc (CRL: 74 mm) human fetal brain stained for GFAP (A) and S100 (B) shown at low magnification. (A) Note the GFAP‐positive staining of the entire VZ except the GE. Also that CHP and midline raphe (R, arrow) are negative. The framed area is shown in higher magnification in Fig. 3A. (B) The neighboring section immunostained for S100 depicts absence of S100‐reactivity in VZ outside the immunopositive DA and fimbria. The midline raphe (R) of the brainstem shows strong immunoreactivity for S100. The boxed area is shown in higher magnification in Fig. 3C together with other astroglial markers. CHP, choroid plexus of the lateral ventricle; DA, dentate anlage; F, fimbria; GE, ganglionic eminence; LV, lateral ventricle; R, raphe; T, thalamus; VZ, ventricular zone. A and B – same magnification. Scale bar: (A) 5000 μm.