The narwhal, a type of toothed whale found in Arctic waters, is famous for its long, spiraled tusk. Once thought to be a unicorn horn, the tusk is actually the left canine tooth of male narwhals, which grows through the upper lip and twists as it extends. In rare cases, both canines of males or the left canine of females may also grow and twist in the same leftward direction. A recent study published in Nature Communications has uncovered the unique internal structure of this tusk, revealing a fascinating arrangement of two spirals with opposite directions. Studying narwhals is challenging due to their Arctic habitat and deep diving behavior, which makes them difficult to observe. To understand the tusk's structure, scientists from various disciplines collaborated using advanced tools at three European synchrotron facilities in Switzerland, France, and Sweden. The research used two tusk specimens obtained from Inuit hunters in Greenland, in compliance with local laws. The tusk consists of two layers: an outer layer made of cement and an inner layer of denser dentin. Although these layers differ in structure and porosity, they are both composed of the same microscopic mineralized collagen fibers. These fibers are mostly aligned along the tusk's length but show a slight, consistent deviation. Using a technique called tensor tomography, scientists visualized the tusk's 3D structure and discovered two internal spirals—one twisting to the left in the cement layer and the other to the right in the dentin layer. This double helix structure, with opposing spirals, provides the tusk with strength and stability, preventing it from twisting excessively in one direction. The design is similar to the structure of the Venus' flower basket, a marine sponge known for its resilience against bending and twisting forces. Researchers now aim to study growth bands within the tusk to understand the narwhal's life history, including how environmental conditions may have affected its development over time. These growth bands could offer valuable insights into past Arctic climates and the challenges narwhals have faced throughout their lives.