Fig. 2 . Proliferation and differentiation in mouse small intestine. The proliferating compartment of an intestinal crypt of an adult mouse small intestine, as revealed by Ki67 immunohistochemistry (brown), which stains proliferating cells, and Alcian Blue staining, which detects mucosecretory differentiated cells. Image courtesy of Verónica Rodilla and Lluís Espinosa.