Armies of cells that make up the body's immune system help to protect it from infection. These bright green masses are immune cells called macrophages, which form the body's first line of defense.
Macrophages can detect bacteria and viruses, and warn other cells of potential threats. In some cases, like in this image, they consume the threat and self destruct.
The lone blue ring to the right of this image is a cell nucleus and is all that remains after a macrophage has 'taken one for the team'. The adjacent red dot is called an ASC speck, which indicates that the macrophage called for backup in its final moments.
Understanding how cells protect the body helps researchers to design better treatments for patients with disorders of the immune system such as arthritis.