Palaeomicrobiology—the study of past microorganisms—is a rapidly emerging field of research. The discovery that ancient microbial DNA can be preserved within archaeological dental calculus has opened the door to investigating changes to dental microbiota (and individual microbial genomes) throughout human history. In this talk I will introduce this nascent field, highlighting the prospects, pitfalls, and challenges remaining. I will share the latest methodological advances, and present new findings relating to changes of dental microbiota and genomes through time.