Breathing gills are a means for sentient species to breathe (or, more accurately, respire) in atmospheres or substances other than their natural one. Some species possess the gills naturally, while other gills are genetically engineered. Typically, however, the gills are surgically implanted, usually in the neck for most humanoid species. G'Kar had them surgically installed into his neck to aid in the breathing of other atmospheres. Lyta Alexander had been surgically altered with breathing gills in her time before returning from Vorlon space in 2260.