A Petri dish is a shallow glass or plastic cylindrical lidded dish that biologists use to culture cells.
Glass Petri dishes can be re-used by sterilization (for example, dry heating in a hot air oven at 160 °C for one hour); plastic Petri dishes must be disposed of after one use.
For microbiology, agar plates are very frequently used (where the dish is filled with warm liquid agar). After the agar solidifies, the dish is ready to receive a microbe-laden sample. Empty Petri dishes may be used to observe plant germination or small animal behaviour, or for other day-to-day laboratory practices such as drying fluids in an oven and carrying and storing samples.