The atom is most definitely not the smallest particle and most definitely can be broken down into smaller pieces; even the protons and the neutrons that we considered to be fundamental particles in and of themselves can be broken down into smaller particles. In an attempt to open your minds beyond the delusion that the atom cannot be broken down, this chapter is to convey and communicate the building blocks of the building blocks of atoms, which we have alluded to oftentimes in previous chapters but have not covered in-depth. Welcome to the wondrous world of quarks.

References
Fifty Years of Quarks - CERN
https://home.cern/news/news/physics/fifty-years-quarks
Quark - Wikipedia
https://en.wikipedia.org/wiki/Quark
Particle Zoo (1960s) - Wikipedia
https://en.wikipedia.org/wiki/Particle_zoo
Flavour (Particle Physics) - Wikipedia
https://en.wikipedia.org/wiki/Flavour_(particle_physics)
Quark Model - Wikipedia
https://en.wikipedia.org/wiki/Quark_model
Pauli Exclusion Principle
http://hyperphysics.phy-astr.gsu.edu/hbase/pauli.html#c2
Spin Classification of Elementary Particles
http://hyperphysics.phy-astr.gsu.edu/hbase/Particles/spinc.html
Up Quark - Wikipedia
https://en.wikipedia.org/wiki/Up_quark
Down Quark - Wikipedia
https://en.wikipedia.org/wiki/Down_quark
Strange Quark - Wikipedia
https://en.wikipedia.org/wiki/Strange_quark
Charm Quark - Wikipedia
https://en.wikipedia.org/wiki/Charm_quark
Bottom Quark - Wikipedia
https://en.wikipedia.org/wiki/Bottom_quark
CP Violation - Wikipedia
https://en.wikipedia.org/wiki/CP_violation
Top Quark - Wikipedia
https://en.wikipedia.org/wiki/Top_quark