Bacteriophages, also known as phages, are viruses that infect and replicate in bacteria. New bacteriophages are being discovered at an astounding rate via both phage isolation studies and metagenomic analyses. In addition, a nucleotide sequence-based viral taxonomic system has been developed to better handle this wealth of new information. As a result of these developments, phage scientists are transitioning from knowing that there must be huge numbers of diverse kinds of phage particles in natural environments to identifying the actual abundance and phage diversity that is present in specific environments. In their new chapter titled "Structural and Genomic Diversity of Bacteriophages" published in the ebook Bacteriophages, Dr. Bert Ely, former undergraduate student Jacob Lenski, and graduate student Tannaz Mohammadi, document the beginning of this transition, offering a glimpse into the magnitude of change unfolding in the field.