The subventricular zone of a mouse brain. This is the largest region where new neurons are born. The blood vessels (green) are important in regulating the behavior of neural stem cells, providing a vascular niche for neurogenesis.

Image courtesy of Terry Burns, Stanford University.

A single mast cell enters conjunctival tissue in the eye in response to an inflammatory agent or pathogen. Mast cells are among the first cells of the immune system to react to the presence of an invader, facilitating movement of leukocytes and other immune cells toward the site of infection through the release of histamines (red dots), which act as chemical messengers.

Image courtesy of Donald Pottle, The Schepens Eye Research Institute, Massachusetts.

The adult mouse hippocampus, a region of the brain involved in learning and memory, is depicted. Reactive astroglia cells (pale yellow) have proliferated and enlarged in response to neuronal activity over time.

Image courtesy of Sandra Dieni, Albert-Ludwigs University, Germany.

Connective tissue is the most abundant and diverse tissue type in the human body, colorfully illustrated here with five different fluorescent proteins.

Image courtesy of Daniela Malide, NIH.

Apoptosis is a form of programmed cell death used to eliminate damaged, infected or unnecessary cells. In this image, serum arrested L-1210 leukemia mouse cells engage in spontaneous apoptosis after nutrient depletion and acid hydrolysis.

Image courtesy of Frank Abernathy.

The genus Drosophila (fruit flies) are among science’s most used animal models, employed by researchers at all stages of the insects’ life. The larval stage depicted covers the first five days after an egg is laid. Three growth phases later, the larva will pupate.

Image courtesy of Chun Han, UC San Francisco.

A false color scanning electron micrograph depicts the microvasculature of a kidney. Red blood cells are colored blue.

Image courtesy of Ruben Sandoval.

The small intestine of a mouse on the 15th day of embryonic development.

Image courtesy of John Hatch, National Heart, Lung and Blood Institute, NIH.

A ring nematode (Mesocriconema sp.). While the nematode C. elegans is a broadly used and useful model organism in research, ring nematodes are plant-parasites that feed on agricultural crops.

Image courtesy of Jonathan Eisenback.

A thin-melt specimen of hippuric acid, a natural metabolite found in human urine. It acts as a biomarker for dietary polyphenol intake (fruits/vegetables) and gut microbiome activity, with levels rising after consuming tea, wine and fruit.

Image courtesy of Brian Johnston.