In this Video, Ms. Poonam Rajawat, Assistant Professor, Biyani Group of Colleges, describes about virus plaque assay. It is an assay to enumerate phage particle on solid agar media. A clear area formed on agar media known as Plaque. It is a double layered technique. Phage dilution was prepared in trypton broth and two drops of E. coli. were added when bacteriophage affect the bacteria, it causes lytic cycle and form plaque.