A flagellum (plural: flagella) is a whip-like structure that protrudes from the cell body of certain microorganisms, such as bacteria and protozoa, allowing them to move through liquid environments. It is composed of microtubules and is powered by a motor protein that facilitates its movement. In eukaryotic cells, flagella are typically longer and more complex than those found in prokaryotic cells. Flagella play a crucial role in locomotion, helping organisms navigate their surroundings.