It occurs when a bigger mass makes stronger gravity, which overwhelms the resistance to compression and forces electrons to merge with protons, creating a solid mass of neutrons. It weighs 10 million tons per thimbleful - beyond human comprehension. And a black hole is the ultimate gravitational collapse, squeezing matter much, much denser. If planet Earth were compressed to its Schwarzchild radius, at which a black hole begins, it would be the size of a pearl . Although electrons peacefully occupy every atom of your body, they're violent when detached.
Lightning bolts are cascades of electrons.
In most atoms, electrons are in pairs with opposite spin, neutralizing them. But in iron-type atoms, some electrons aren't paired, and the unbalanced spin makes each atom a magnet. When we look at some stars, we're seeing light that left them hundreds or thousands of years ago. Our eyes see the past. This seems impossible, but many tests have verified it.