Step 1: Recall the cell organelle function.
Cells need ATP as their usable energy currency. The organelle that produces most ATP during aerobic respiration is the mitochondrion.
Step 2: Match the nickname.
Because mitochondria release energy from food molecules and make ATP, they are called the powerhouse of the cell.
Step 3: Pick the correct organelle.
The correct answer is mitochondria.
\[ oxed{ ext{Option 3: Mitochondria}} \]