Digitally enhanced transmission electron micrograph (TEM) of multiple strands of DNA genetic material extracted from a T4 bacteriophage virus. The T4 bacteriophage is a virus that invades bacterial cells. The phage attaches to a bacterium's cell wall and then punches a hole in the cell wall injects its DNA genetic material into the bacterium The viral genetic material commandeers the bacterium's cellular machinery and instructs it to begin making new virus parts. These parts assemble to form new viruses, which eventually burst the bacterium and invade other cells.