In medium-sized stars such as the sun, nuclear fusion almost always means the ,hydrogen, nitrogen) of nuclei to ,lithium, helium) , but larger stars can produce elements as heavy ,silver, iron)

Nuclear fusion is the process of combining two lighter nuclei into a  single heavy nucleus (part of an atom). This process is also called a nuclear reaction and it releases a large amount of energy. In medium-sized stars such as the Sun, nuclear fusion almost always means the fusing of hydrogen atoms to form helium, but larger stars can produce elements as heavy as iron. 

there are so many examples for that in different areas, like biology experiment carried out in our lab recently.

here's one link: