Light micrograph of the developing kidneys of a foetus showing primitive renal corpuscles located around the outer cortex. Developing renal tubules and collecting ducts converge medially towards the large empty space termed the renal pelvis. In the postnatal kidney urine passes into the ureter via the pelvis. The aorta and inferior vena cava are seen in the midline, and a developing cartilaginous vertebral body and nucleus pulposus are stained blue. Paraffin section, alcian blue, and haematoxylin and eosin stain. Magnification: x16 when width printed at 10cm.