The mitochondria is the part of the cell that forms ATP. It's often referred to as the "powerhouse of the cell" because it's responsible for cellular respiration, the process that generates ATP, the primary energy currency of cells.

Here's a breakdown:

* Mitochondria have a unique structure with an inner and outer membrane, creating compartments called the intermembrane space and the mitochondrial matrix.

* Cellular respiration happens in these compartments, involving a series of chemical reactions that break down glucose (a sugar) and release energy.

* This energy is then used to convert ADP (adenosine diphosphate) into ATP (adenosine triphosphate).

While other cellular components like the cytoplasm also play roles in energy production, the mitochondria are the primary site of ATP synthesis.