![A male Rufous Hummingbird in profile perched on the tip of a budding branch.](https://media.audubon.org/image/engagement-cards/rufous_hummingbird_boebatyapa_1200x657.jpg?width=345&height=219&auto=webp&quality=10&fit=crop&enable=upscale&blur=100)
Locked within the beautiful blue plumes of a blue jay or common kingfisher is the solution to a physical mystery. Ornithologists and physicists have discovered that these non-iridescent azure hues are created by the intricate, spongelike nano-architecture of the birds’ feathers. “These structural colors never fade with time,” says Vinod Saranathan of Oxford University. By mimicking these natural templates, engineers can create myriad applications, from eco-friendly, nontoxic dyes and cosmetics to lasers and more efficient fiber-optic cables.