Chances are you’ve heard of probiotics: supplements delivering ‘good microbes’ to the gut, providing a wide range of health benefits. You may also be aware of prebiotics: supplements designed to fuel the good microbes already living in our guts. The next wave of gut-health supplements, known as synbiotics, essentially combine pre- and probiotics. To keep research and development on the right track, an expert panel recently redefined the term and developed guidelines on scientific investigation.