Recent reports suggest that many tumours, in particular those close to the gastrointestinal tract harbour a characteristic microbiota. However, the etiological roles of individual microbes, some of which have been shown to invade host cells, produce genotoxins, or reprogram antitumor immunity, remain poorly understood. We have worked on unravelling the composition of intra-tumoral microbes in several cancer entities through both sequencing and imaging-based methods. We aim to further investigate the cellular and molecular interactions between tumour-resident microbes and host cells and their molecular programs by integrating microbiome-specific assays with host readouts, such as RNA-Seq. Our research was initially focused on colorectal cancer and now increasingly extends to probing the presence and influence of microbes in other tumour entities.