While probiotics have been on the market long enough that people are familiar with what they are and how they work, prebiotics are a little less familiar to many. Probiotics are bacteria and yeasts that naturally reside in our guts and help keep our digestive system healthy and safe from harmful, opportunistic pathogens. Prebiotics are the food for probiotics. Beneficial strains in our microbiome get food from what we eat, but prebiotic supplementation ensures that they have plenty of food to thrive.