Cilia are tiny, hair-like structures that extend from the surface of many cells. They play a crucial role in movement and sensing the environment. For example, in the human respiratory system, cilia help sweep away dust and mucus, keeping our airways clear and healthy. In addition to their role in humans, cilia are also found in many other organisms, such as paramecium, a single-celled organism that uses cilia to swim through water. These structures can be found in various forms, serving different functions, but their primary purpose is to aid in movement and communication within the cell's environment.