Darwin's ideas about the origin of coral reefs led him eventually to the theory of evolution.
The coral polyp may be a humble creature, but under the right conditions it is immortal.
Steve explains its connection with stem cells.
The coral polyp appears to be one creature, but frequently it is two, living symbiotically with its own solar panel.
This offers some insights into the origins of the human cell.
Coral reefs may have a role to play in the struggle to contain global warming.