Gobies are fish of the family Gobiidae, one of the largest fish families comprising more than 2,000 species in more than 200 genera. Most of them are relatively small, typically less than 10 cm (3.9 in) in length. Gobies include some of the smallest vertebrates in the world, such as Trimmatom nanus and Pandaka pygmaea, which are under 1 cm (3⁄8 in) long when fully grown. Some large gobies, such as some species of the genera Gobioides or Periophthalmodon, can reach over 30 cm (0.98 ft) in length, but that is exceptional.