Great Barrier Reef
This image of a coral reef was taken by NOAA photographer LCDR Eric Johnson on the Great Barrier Reef off the eastern coast of Australia. The Great Barrier Reef is the world's largest coral reef system composed of over 2,900 individual reefs and 900 islands stretching for over 1,400 miles (2,300 kilometers). It is the world's biggest single structure made by living organisms and can even be seen from space. It is ironic that this gigantic structure was built by some of the world's tiniest organisms, coral polyps.