Daniel thinks seashells are just little rocks the ocean makes.

They are not.

Every shell you have ever picked up on a beach was built by a living animal -- layer by layer, from materials taken from the surrounding seawater. The animal never found it. Never moved into it. It grew it, from scratch, as part of its own body.

This episode explains how -- and where shells go after the animal is gone.

What you will find in this episode:

• What the mantle is and how a mollusk builds a shell from calcium carbonate
• Why spiral shells grow the way they do -- and what a logarithmic spiral actually is
• How genes control shell colour and pattern -- and what shell chemistry can reveal about ancient oceans
• Why the shells on beaches are usually empty -- and why you should check before you pick one up
•  ...