Human intestinal epithelial cells cultured in the Wyss Institute’s human-gut-on-a-chip form differentiated intestinal villi when cultured in the presence of lifelike fluid flow and rhythmic, peristalsis-like motions. Here the villi are visible using a traditional microscope (left) and a confocal microscope (right). Fluorescent antibodies stain the nuclei blue and their specialized membranes, known as apical brush borders, green. 