There’s another way of making a structure. A shell structure is just made of a thin, curved outer layer and it’s hollow inside. Like this, or this, or this, or this. A shell structure doesn ...

A thin, tubelike structure called a siphuncle pumped air through the interior chambers of the shell, which scientists believe helped provide buoyancy and move ammonites through the water.

The parrot's brain has a nested 'core and shell' structure for vocal learning. Neurons in the shell surrounding the established vocal centers of the parrot brain play a part in vocal learning and ...