A petri dish is a shallow, lidded, transparent container, typically cylindrical and made of plastic or glass, used to culture microorganisms and cells on a nutrient-rich agar substrate in a sterile environment. Invented by German microbiologist Julius Richard Petri, these dishes facilitate the growth, observation, and study of bacteria, fungi, and other cells in fields like microbiology and cell biology. They are available in disposable (often polystyrene) and reusable (glass or polycarbonate) forms, with variations like vented lids for gas exchange and different compartment designs for specific applications.