Figure 1. The Madaba mosaic from the sixth century, part of the floor of the early Byzantine Church of St. George in Madaba, Jordan. This is the earliest cartographic depiction of Jordan and Israel. The walled city of Jerusalem can be seen below the Dead Sea. (Photograph: Daniel Graepler and Marianne Bergmann, Archeological Institute of the University of Goettingen, Goettingen, Germany.)

Figure 2. Dense population of the giant tube worms Riftia pachyptila. They are up to 2 meters (7 ft) long and 6 cm (2 in) in diameter. They harbor hydrogen sulfide-oxidizing bacteria. Galapagos, seafloor spreading zone, 0 ° 48’N; depth, 2550 meters (8400 ft). (Holger Jannasch [1927–1998], with permission of Nordrhein-Westfaelische Akademie der Wissenschaften, Duesseldorf, Germany.)

Figure 3. Anaerobic oxidation of methane by a consortium consisting of methanoarchaea (colored red) and sulfate-reducing bacteria (colored green). (Photograph: Antje Boetius, Bremen, Germany.)