Definition
A spicule is a small, needle-like or spike-shaped structure. Imagine tiny splinters, often made of calcium carbonate or silica. They're found in various organisms, like sponges and some marine invertebrates, providing structural support. Think of them as the scaffolding inside a building, only much, much smaller. They can also refer to small, pointed crystals in rocks. Unlike smooth surfaces, spicules offer a prickly defense or reinforcement. They are the hidden armory of the natural world.