Hugenholtz and colleagues adapted the recently developed technique of viral tagging to determine phage–host bacteria pairs in faecal samples from healthy humans. Briefly, they extracted viruses and stained them fluorescently. After binding to bacterial cells, this ‘tag’ was used to single sort and sequence pairs (that is, the bacterial cell and its attached fluorescent phage cargo). The authors identified 363 unique pairs, including some with previously unknown phages. Interestingly, the majority of phages could not bind more than one host species, making them unlikely agents of horizontal gene transfer between species in the human gut. However, phages from one donor could target over 40% of bacterial cells from another donor despite microbiome differences between the donors, which has implications for faecal microbiota transplantation.