Silverfish are the smallest mob in Minecraft. They appear when the player mines a certain block. The block, named Block Number 97, is available in Creative Mode as a Stone (or Cobblestone) Monster Egg. These only spawn in Extreme Hills Biomes or Extreme Hills Edge biomes. They also appear in Strongholds, where there are Silverfish spawners. Silverfish also drop no reward for killing them aside from experience. Silverfish were the basis for Endermite's and Redstone Bug's design.