The flagellum is a long tail like organelle that some cells use to move in there environment . Both prokaryotes and eukaryotes cells can have a flagellum. The flagellum is attached in between the plasma membrane of a cell. The flagellum is made of special proteins the allow the tail to spin in circles; through either ATP energy for eukaryotic cells, or ionic forces in prokaryotic cells. The flagellum is very useful for cells to move to a different environment which can contain more nutrients or have more hospitable conditions. A good example of a flagellum would be a sperm cell with it’s long tail like organelle which is used to swim to a egg to fertilize.