We reviewed the evolution of stars much more massive than the Sun, from the point when they've consumed all their fuel. The 'onion ring' model shows us that all elements heavier than hydrogen and helium were produced in nuclear processes inside massive stars. When the star becomes unstable due to the cessation of fusion, the massive envelope collapses onto the iron core. Two things happen next: the intense gravitational field compresses the core even further, so it becomes either a neutron star or a black hole, depending on the initial mass of the star, and the outer envelope slams onto the core and then back into space, creating a supernova explosion.