PET is a small suite of tools meant to assist in the research and identification of bacteriophages. It provides visualizations of known phages based on the behavior of restriction endonucleases on the phages' DNA sequences, as well as custom phylogenetic trees based on these data. The Unknown Phage Visualization tool can help identify an unknown phage by comparing results of actual enzyme applications to an unknown phage against the values in the database of known phages.