Nestled among giant fish tanks at the California Academy of Sciences, there's a black box—just big enough to hold six aquariums and maybe five humans. What it lacks in size, though, it makes up for in preciousness: Running here is a experiment that could help save corals from annihilation. The corals in these tanks are reproducing sexually. Which is weird, because even out in the wild, coral spawning is a fragile process, easily disrupted by changes in temperature and acidity.