Cilia and flagella are cellular structures that play a crucial role in cell movement. Cilia are short, hair-like projections that cover some cells and facilitate movement across surfaces or in fluid, while flagella are longer and typically exist as a single or few structures per cell, propelling the cell through liquid environments. Both are composed of microtubules and enable various organisms, from single-celled ones to multicellular entities, to navigate their surroundings effectively.