They’re identical twins. They’re from Australia. And they’re trying to teach the world about the fragility of coral reefs, one crochet stitch at a time. A few years ago, Christine and Margaret Wertheim experimented with using crochet to illustrate a geometry concept called hyperbolic space. When they injected some randomness into the patterns, the darning duo noticed that their creations—wispy, colorful, structured yet chaotic—began to resemble a coral reef. “It’s as if they were going through evolution,” Margaret says. The sisters set up a website, the art press picked it up, and before long the Hyperbolic Crochet Coral Reef Project went viral: More than 3,000 volunteers wielded hooks and yarn to create an array of specimens, which can fill a 4,000-square-foot exhibit space. The sisters hope their work imparts an appreciation for the plight of corals. “We can probably live without the reefs,” Margaret Wertheim says. “But no one knows what the cascading environmental effects will be on the millions of species that rely on them.” The hand-stitched sea simulacra are currently on exhibit at the Cooper-Hewitt Museum in New York and will debut at the Smithsonian in D.C. in October. Check it out if your knowledge of marine biology is fuzzy.