In the summer, many people enjoy walks along the beach looking for seashells. Among the most prized are those that contain iridescent mother of pearl (also known as nacre) inside. But many beachcombers would be surprised to learn that shimmery nacre is one of nature’s strongest, most resilient materials. Now, researchers have made a material with interlocked mineral layers that resembles nacre and is stronger and tougher than previous mimics.