Fresh after the Big Bang, the Universe fizzed like a freshly poured soda. All of space was filled with bubbles — regions of new vacuum, the kind governed by the Standard Model, pushing out the old unstable state. The walls of these bubbles accelerated to near light speed, and in head-on collisions they crumpled and burst, unleashing monstrous energy.
These collisions acted as a colossal natural accelerator: at the point of impact, particles of unimaginable mass were born. Among them were candidates for dark matter and hypothetical right-handed neutrinos. The latter, as they decayed, produced a microscopic excess of matter over antimatter — the very imbalance from which galaxies, stars, and we ourselves later formed. This was the one and only time nature switched on such a powerful collider; those conditions never repeated, but we see the results today in the form of galaxies and dark matter.
Some of the particles born could weigh as much as a grain of salt — an absolute record in the world of elementary particles, since an ordinary proton is billions of billions of times lighter.
In science fiction, vacuum decay usually appears as a cosmic catastrophe — for example, in Stephen Baxter's novel 'Vacuum Diagrams'. Yet in reality, it is precisely this process that may have given birth to everything that exists.