Corals are of a great value to societies worldwide. Not only do they provide a beautiful, natural ecosystem for tourism, generating billions of dollars of income annually, but they also protect coastlines from turbulent waves and storms and are a critical habitat for many marine animals. Due to anthropogenic stressors, coral reefs are in a calamitous worldwide collapse. Rising sea temperatures cause the corals to expel their essential symbiotic algae, a process called “bleaching” that often results in death. Coral-associated bacteria and other microbes are also affected by warming oceans, but much less is understood their role in the coral’s response to heat stress. However, we are beginning to understand the ways in which corals recognize the presence of microbes to coordinate immune responses. By studying this phenomena, we can better understand coral health and the harmful effects of bleaching, and disease.