A flagellum is a whip-like structure that allows a cell to move. They are found in all three domains of the living world: bacteria, archaea, and eukaryota, also known as protists, plants, animals, and fungi. While all three types of flagella are used for locomotion, they are structurally very different. Flagella are used not only for movement, but also for aiding in cell feeding and eukaryotic reproduction. Flagella use intraflagellar transport, which is the transport of a complex of proteins required for the signaling molecules that give flagella mobility.