As a spiritual successor to Kurumi no naka ni wa (Inside a walnut), which mixed a boundless imagination with the growth of a tree, Yuko Takao presents this book about seashells and how fossils are made. If you shake a shell and it rattles, that means there are tiny, little treasures inside. If a shell floats, that means it’s a tiny, little boat from a far-off country. But what if it’s more like a rock than a shell? That means it’s a shell that lived millions of years ago and became fossilized as sand and mud settled over it. Shells tell the story of the sea, and Takao illustrates it beautifully.