You may know about the vital public health services performed by the U.S. Centers for Disease Control and Prevention (CDC). But did you know that the CDC is also a fount of free images?

Media produced by federal employees in the line of their official duties are usually destined for the public domain. As a result, the agency's Public Health Image Library (PHIL) hosts a trove of images that can be used openly, without prior permission, for anything from science blogging to t-shirt design.

Below is a sampling from the CDC's electron microscopy files.

This electron micrograph depicts an amoeba, Hartmannella vermiformis (orange) as it entraps a Legionella pneumophila bacterium (green) with an extended pseudopod. Credit: CDC/Barry S. Fields.

A scanning electron micrograph (SEM) shows the ventral surface of a Giardia muris trophozoite, the intestinal parasite responsible for Giardiasis. Credit: CDC/Stan Erlandsen.

This digitally-colorized scanning electron micrograph (SEM) reveals some of the ultrastructural morphology displayed on the ventral surface of a bedbug, Cimex lectularius. Credit: CDC/ Janice Haney Carr.

This transmission electron micrograph (TEM) reveals Rubella virions in the process of budding from the host cell surface to be freed into the host’s system. The Rubella virus is known to be the cause of measles. Credit: CDC/Fred Murphy/Sylvia Whitfield.

This digitally-colorized scanning electron micrograph reveals morphological differences between normal red blood cells and a sickle cell (left) found in a blood specimen of a patient with sickle cell anemia. Credit: CDC/Janice Haney Carr.

The compound eye of a butterfly as seen through a scanning electron microscope. Credit: CDC/Janice Carr.

False color scanning electron micrograph of antibiotic-resistant Staphylococcus bacteria. Credit: CDC/Matthew J. Arduino.

This digitally-colored scanning electron micrograph depicts a grouping of numerous Gram-negative, anaerobic, Borrelia burgdorferi bacteria, the pathogen behind Lyme disease. Credit: CDC/Janice Carr.

Scanning electron micrograph of a human body louse, the vector of Typhus. Credit: CDC/Joseph Strycharz/Kyong Sup Yoon/Frank Collins.

A colorized negative stained transmission electron micrograph depicts ultrastructural morphology of the A/CA/4/09 swine flu virus. Credit: CDC/C. S. Goldsmith/A. Balish.

For more of the CDC's images, visit PHIL.