What is the "powerhouse" of the Eukaryotic animal cell?

The story behind the answer

Mitochondria are called the cell’s “powerhouses” because they produce most of the cell’s ATP—the energy currency—through cellular respiration. Inside their highly folded inner membranes, electrons flow through the electron transport chain and drive ATP synthase to convert the energy from sugars and fats into usable ATP. That’s why, unlike the nucleus (information storage), endoplasmic reticulum (assembly and transport), or chloroplasts (photosynthesis in plants), mitochondria supply energy for animal cells’ work.

Fun fact: Mitochondria likely began as free-living bacteria that merged with early cells (endosymbiotic theory). They still carry their own circular DNA, have a double membrane, and are mostly inherited from your mother. Memory tip: “Mighty-chondria make mighty amounts of ATP.”