Question: What is the smallest thing a thing that is even smaller than things inside a proton?

David Walker-Sünderhauf answered on 13 Mar 2019:

This really isn’t my field of expertise, but particles inside atoms (electrons, protons, and neutrons) are all made up of even smaller particles called quarks. These come in several flavours or type – I think the most common ones are up-quarks and down-quarks. Quarks themselves are made up of even smaller particles, and these again in turn are made up of smaller particles. I think the latest state of knowledge is that the smallest ones are called “strings”. I think Oliver would probably know more about this!