Mitochondria are organelles found in eukaryotic cells that are essential for aerobic respiration. They have two membranes that create three distinct compartments - the outer membrane, inner membrane, and matrix. The inner membrane folds inward creating cristae where the electron transport chain is located. Mitochondria contain their own circular DNA and 37 genes. Their primary function is to produce energy through oxidative phosphorylation where nutrients are broken down and ATP is generated to power the cell.