Here's why:

* Nuclear fusion is the process where two light atomic nuclei combine to form a heavier nucleus, releasing enormous amounts of energy.

* The most common fusion reaction is the fusion of two hydrogen isotopes, deuterium and tritium, to form helium and a neutron.

* This reaction is the basis of the hydrogen bomb and is also the process powering stars, including our sun.

While other elements can be produced through nuclear fusion, helium is the most common and fundamental product.