Human small intestine showing villi and glands. The cytokeratinin the cells is stained blue, the cell nuclei are stained red and the endothelial cells lining the blood vessels are stained green.

Licence: Attribution 4.0 International (CC BY 4.0)

Credit: Human small intestine showing villi and glands. The cytokeratinin the cells is stained blue, the cell nuclei are stained red and the endothelial cells lining the blood vessels are stained green. S. Schuller. Source: Wellcome Collection.