A lung was a major internal organ. For those organisms which possessed lungs, the organs played a vital role in the breathing and respiration processes. Most species, including Humans, had two lungs, though members of the Bith species had only a single lung, a puncture to which was fatal if untreated. The Gungan species had strong and sturdy lungs which allowed them to hold their breath for extended periods, enabling them able to travel freely to their underwater cities.