Replica plating is a technique in which multiple dishes, also known as Petri plates, containing solid (agar-based) microbial media, are inoculated with between thirty and three-hundred colonies of microorganisms from a primary plate (or master dish), reproducing the original spatial pattern of colonies. The technique involves pressing a velvet-covered disk to a primary plate, and then imprinting multiple secondary plates with cells in colonies removed by the velvet from the original plate. By using different types of selective growth media (lacking nutrients or containing chemical growth inhibitors such as antibiotics) on the different secondary plates, it is possible to rapidly screen a large number of individual isolated colonies and detect those that have different phenotypes.