The cell organelle known as the "powerhouse of the cell" is the mitochondrion.

Here's why:

* Energy Production: Mitochondria are responsible for cellular respiration, the process that converts glucose into ATP (adenosine triphosphate). ATP is the primary energy currency of cells.

* Metabolic Activity: Mitochondria also play a role in other metabolic processes, such as amino acid metabolism and fatty acid oxidation.

While other organelles contribute to cell function, the mitochondria are the primary site of energy production, earning them the nickname "powerhouse of the cell."