In 2016, Josiah Zayner, a former synthetic biology research scientist at NASA, checked himself into a hotel room. Over the course of four days, he performed an extremely risky experiment on himself. The goal: “To completely replace all of the bacteria that are contained within my body.” Gut Hack, a short documentary by Kate McLean and Mario Furloni, chronicles Zayner’s attempt to transplant his microbiome in order to relieve himself of a lifetime of debilitating gastrointestinal problems.