The main role of mitochondria in eukaryotic cells is to generate adenosine triphosphate (ATP), the cell's primary energy currency. Often referred to as the "powerhouse of the cell," mitochondria are responsible for the process of cellular respiration, where glucose and oxygen are utilized to produce ATP, carbon dioxide, and water. Mitochondria also play roles in metabolism, apoptosis, and the regulation of cellular signaling, making them crucial for overall cell function and health.