Stars are furnaces to forge atoms

The furnace is a star. In our sun (it is a star, yeah) hydrogen is constantly burning into helium.

This is how two hydrogen atoms fuse to create a helium atom.

Simple, light weight atoms can build up in smaller stars, but more complex atoms, like iron with 56 protons, need a superstar, to be more exact, a supernova. It is a very big star, bigger than our sun, which has exploded and the extreme heat from the explosion created a lot of rare atoms.

[blender src="https://patchlessons.com/wp-content/uploads/2019/09/iron.html" width="100%" height="500"] [/blender]

It is the model of an iron atom. Of course, protons and electrons don't have colours, they are not like balls, but the numbers are correct.