Research has shown that gut microbes can influence several aspects of the host's life, including aging. Given the complexity and heterogeneity of the human gut environment, elucidating how a specific microbial species contributes to longevity has been challenging. To explore the influence of bacterial products on the aging process, researchers at Baylor College of Medicine and Rice University developed a method that uses light to directly control gene expression and metabolite production from bacteria residing in the gut of the laboratory worm Caenorhabditis elegans.