Florida's coral reefs are under siege. Since 2014, Stony Coral Tissue Loss Disease (SCTLD) has spread rapidly across the Florida Reef Tract and Caribbean, killing vast numbers of reef-building corals and leaving behind dead skeletons where once-thriving reefs supported diverse marine life. Despite the severity of the crisis, little is known about how these diseases affect the microscopic structure of coral skeletons—the pores, densities and thicknesses that give reefs their strength and resilience.