Motility in Bacteria is due to presence of thin extensions called as Flagella. The number and arrangement of flagella varies in different types of bacteria. Flagella is made up of three main parts: Filament: Longest and main part that extends from cell surface to the outside and is composed of flagellin protein. Hook: Structure near the cell surface. Basal body: A system of rings embedded in cell envelope. The eukaryotes also possess flagella but these are structurally different from that of the prokaryotic flagella. Their core called the axoneme, possesses a number of microtubules running parallel to the long axis. The axoneme usually has nine pairs of doublets of radially arranged peripheral microtubules, and a pair of centrally located microtubules. Such an arrangement of axonemal microtubules is referred to as the 9+2 array. The central tubules are connected by bridges and is also enclosed by a central sheath, which is connected to one of the tubules of each peripheral doublets by a radial spoke. Thus, there are nine radial spokes. The peripheral doublets are also interconnected by linkers.