Petri dishplugin-autotooltip__default plugin-autotooltip_bigPetri dish: a round dish, usually 5-10 cm in diameter, that can contain growth media to grow cells in vitro.: a round dish, usually 5-10 cm in diameter, that can contain growth media to grow cells in vitroplugin-autotooltip__default plugin-autotooltip_bigIn vitro: taking place outside of a living organism, usually in a test tube or Petri dish..