nature · FOLLOW YOUR CURIOSITY
Rock, plant… or a whole neighbourhood of animals?
Meet the tiny builders behind a coral reef.
Explore the interactive discovery →
Three layers of a reef
Tap each idea to explore its role.
Polyp
A polyp is a small animal with tentacles.
Skeleton
Stony corals produce a calcium-carbonate skeleton.
Colony
Many connected polyps can form a colony.
What you just noticed
A hard surface can conceal living tissue. Reef-building corals leave skeletons that contribute to structures much larger than an individual animal. Not every coral builds a reef.
Keep the distinction
See what happens
The reef’s architecture begins with tiny living builders.
Stony corals produce a calcium-carbonate skeleton.
AN IDEA TO TAKE WITH YOU
The reef’s architecture begins with tiny living builders.
Follow a connection
How much coastline can you hide in a single line? →
How does scale change the coast you see?
Sources and transparency
NOAA · What are corals?
Accessed: 2026-10-28
Smithsonian · Ecosystem engineers
Accessed: 2026-10-28
Prepared with AI assistance. Illustrations are explanatory, not evidence. You can report an issue in the interactive discovery.