Mitochondria are often called the "powerhouses" of the cell because they produce energy. They convert the food we eat into a form of energy that our cells can use, known as ATP (adenosine triphosphate). This process is essential for all living organisms, as it fuels everything from muscle movement to brain function. In addition to energy production, mitochondria play a role in other important functions, such as regulating cellular metabolism and controlling cell death. They have their own DNA, which is different from the DNA found in the nucleus of the cell, highlighting their unique role in our biology.