A most unusual exhibit is at the Smithsonian's National Museum of Natural History. The Hyperbolic Crochet Coral Reef is the work of a host of fiber artists from around the world. This whimsical tour de force illustrates hyperbolic geometry, a mathematical concept in which lines bend on a curved plane and can meet themselves. I cannot truly grasp this, but I do understand the curvy beauty of a lettuce leaf or the ruffled edges of coral. The natural world is full of examples of hyperbolic geometry. Chunky yarns, delicate yarns, furry yarns that waft gently in the air currents---a huge variety of fibers have been used to create the coral branches and fans. Crocheted sea kale, jellyfish, starfish and sea urchins inhabit the reef. Some of the artists replicated harder, shinier surfaces by crocheting strips of plastic bags. How appropriate, and also ironic, considering the amount of plastic collecting in our oceans.