Bacteriophages, also known as phages, are viruses that infect and replicate within bacteria. They are the most abundant and diverse biological entities on Earth, with an estimated 10^31 phages in the biosphere. Bacteriophages play a crucial role in ecosystems by controlling bacterial populations and shaping microbial communities. Research in the field of bacteriophages focuses on understanding the molecular mechanisms of phage infection, replication, and evolution, as well as their potential applications in biotechnology, medicine, and agriculture. Bacteriophages have been studied extensively for their ability to selectively target and kill specific bacteria, making them promising candidates for the development of novel antimicrobial agents, known as phage therapy. Additionally, bacteriophages are used in various biotechnological applications, such as phage display, phage biocontrol, and phage-based biosensors. Overall, research in the field of bacteriophages continues to uncover the diverse roles these viruses play in microbial ecosystems and their potential applications in various fields.