The mitochondria, which are the power stations of the cell, produce an energy-storing molecule known as ATP. This molecule is used to power chemical reactions and processes that are essential for life. As cells age, their mitochondria become less efficient at producing ATP, which may play into some age related diseases. Mitochondria are also important in other ways: they regulate various processes in the cell through molecular signals they release, play a key role in apoptosis (cell suicide), and are also a major source of reactive oxygen species. This article explores mitochondria and their relationship with aging in greater detail.