The discovery of (bacterio)phages revolutionised microbiology and genetics, while phage research has been integral to answering some of the most fundamental biological questions of the twentieth century. The susceptibility of bacteria to bacteriophage attack can be undesirable in some cases, especially in the dairy industry, but can be desirable in others, for example, the use of bacteriophage therapy to eliminate pathogenic bacteria. The relative ease with which entire bacteriophage genome sequences can now be elucidated has had a profound impact on the study of these bacterial parasites.