Probiotics can help maintain a healthy gut microbiome or restore populations of ‘good bacteria’ after a heavy course of antibiotics. But now, they could also be used as an effective treatment strategy for certain intestinal diseases, such as Crohn’s disease. Researchers have developed a microgel delivery system for probiotics that keeps ‘good’ bacteria safe while actively clearing out ‘bad’ ones. In mice, the system treated intestinal inflammation without side effects.