A clamshell is a hinged container or device that opens and closes like the two shells of a clam. The term describes anything with two halves connected by a hinge that swing apart and snap shut.

The original clamshells, of course, belong to actual clams: the two hard, protective shells that open to let the clam feed and close to keep it safe. But engineers and designers borrowed this simple, effective design for all sorts of everyday objects. Flip phones were often called clamshell phones because they opened and closed just like a clam. Some laptop computers use a clamshell design. Plastic clamshell packaging, that frustratingly tough clear plastic that holds batteries or toys in stores, got its name from the same hinged structure.

The design works so well because it protects what's inside while staying easy to open and close. When you open a clamshell container for your leftovers, you're using the same mechanical principle that's kept clams safe in the ocean for millions of years.