Just over 500 million years ago, many of the animal forms recognized today suddenly appear in the geologic record. This rapid evolutionary event often is referred to as the Cambrian Explosion, and its causes have remained a mystery for centuries. Interestingly, this period in time is also when we see the first framework reefs in Earth's history. Knowing that coral reefs are crucial to the development and maintenance of biodiversity in today's oceans, I am investigating these ancient reefs to see if they were a crucial element of the Cambrian Explosion. Is it possible that these first reefs provided dense habitat structures similar to modern coral reefs and promoted the original biodiversification of animals on Earth?