Mitochondrion and Cristae
Mitochondria are sometimes described as cellular power plants because their main purpose is to manufacture adenosine triphosphate, which is used as a source of energy for the cell. Mitochondria are very small organelles, you might find cells with several thousand mitochondria. Cristae is the inner membrane of the mitochondria that folds over many times, which increases the surface area of the mitochondria.