The cell organelle known as the powerhouse of the cell is the mitochondrion (plural: mitochondria). Mitochondria play a crucial role in cellular respiration, a process where nutrients are converted into adenosine triphosphate (ATP), the primary energy currency of cells. These organelles have their own DNA, which supports the endosymbiotic theory, suggesting that they were once independent bacteria assimilated into eukaryotic cells. Mitochondria are essential for energy production, regulating metabolism, and apoptosis (programmed cell death). Their efficient functioning is vital for overall cellular health and energy management within all living organisms.