So now you know about almost every particle in the standard model. All that is left is the Higgs boson, which you will see in the last chapter.

## Why do we not see any of these new, heavier particles?

Why are there no atoms made of charm quarks, strange quarks and muons? The answer is that the heavy particles are very unstable, and quickly transform into their lighter brothers. Heavy particles are produced in very high energy collisions, such as in particle accelerator experiments. They are also found in cosmic rays – very energetic particles that fall to Earth from space, and that are produced in places as exotic like the core of the sun or even a supernova explosion.

## Outlook

Why are there so many particles? Why do three generations exist rather than just one? The answer is simple: nobody knows!

And there is more to come: You have probably heard of antimatter, haven’t you? This is what the next chapter will explain.