Most amoebae are microscopic in length, although some amoeboids, such as members of the Chaos family, can grow large enough (up to 5 millimeters) to be seen by the naked eye. Amoebae are unicellular protozoans that live in a myriad of environments.
Such environments typically include ponds and other bodies of fresh water (and some salt water), but the parasitic amoeba Entamoeba histolytica lives in the alimentary tract and causes dysentery in humans. Amoebae have an uncommon form of transportation, using false feet known as pseudopodia. These appendages are made through projecting the cell's cytoplasm and can also be used to engulf prey.