Humans are walking ecosystems – our bodies are host to a wealth of microbial diversity that play an integral role in our health and well-being. The majority of microbes associated with the human body reside in the gut and what I find most fascinating is that every single person has their own unique microbiota that is exclusive to them! Bacteria living in the human gut are continuously exposed to different selection pressures that range from bacteriophages, which are obligate viral parasites of bacteria, to fluctuations in the chemical environment such as a changes in diet or the presence of antimicrobials including antibiotics. My research is focused on understanding how bacteriophages and the chemical environment drives this unique variation in the gut microbiota between individuals and within an individual over their life-time. I am particularly interested in microbial evolution and understanding how microbial adaption to different selection pressures impacts on host health.