The concept of (bacterio)phage therapy is simple; target the phage to the 
bacterial pathogen causing disease. As phages are natural killers of bacteria, 
one could expect this to be an easy task. However, when it comes to phage 
therapy within the gut, it might not be quite that simple. Already without 
exogenous intervention, a multitude of phage-bacterial interactions occur within 
the human gut, some of which might play a direct role in disease progression. In 
this perspective, we aim to summarise the current understanding of phages within 
our gut, moving from infancy, adulthood, and then into disease progression. We 
then highlight recent advances in phage-based interventions, both conventional 
phage therapy and the progressing field of whole virome transplant.