Seashells are so plentiful that you may sometimes take them for granted. Scientists have estimated that just one small stretch of beaches along the Gulf of California contained at least 2 trillion ...

Most of us have picked up a shell or two that caught our eye while strolling the beach, and many of us might even have a small collection of favorites that decorate our shelves and counters at home.

Flashy iridescent shells might not seem like the best evolutionary strategy for bugs trying to avoid hungry birds. But in recent years, biologists have shown that iridescence—lustrous shifts in color, ...