Here's why:

* Mitochondria are often called the "powerhouses" of the cell.

* They are responsible for cellular respiration, a process that breaks down glucose (sugar) and converts its chemical energy into a usable form called ATP (adenosine triphosphate).

* ATP is the primary energy currency of cells, providing energy for various cellular functions like muscle contraction, protein synthesis, and active transport.

While other cellular structures contribute to energy production, the mitochondria are the primary site of ATP generation.