The organelle known as the powerhouse of the cell is the mitochondrion. Mitochondria are responsible for producing adenosine triphosphate (ATP), the energy currency of the cell, through a process called oxidative phosphorylation. This energy production is vital for various cellular functions, including metabolism, signaling, and maintaining homeostasis. Mitochondria have their own DNA and replicate independently, which supports the endosymbiotic theory that they were once free-living prokaryotic organisms. Additionally, they play a key role in regulating apoptosis, or programmed cell death.