Sorry, I was typing that out in a rush earlier - the leptons are electrons, electron neutrinos, muons, muon neutrinos, taus, tau neutrinos, and all of their antiparticles. 6 kinds of lepton with corresponding antiparticles.

I also said there are 6 kinds of quark: up, down, top, bottom, strange, charmed. I should also have said that there are the 6 corresponding antiquarks for each of these.

Notice that there are 6 colours of quark, and 6 kinds of lepton. When particle physicists first discovered the tau and the tau neutrino, they had only discovered the up, down, strange and charmed quarks. Upon discovery of the tau and its neutrino they actually hypothesised that top and bottom quarks existed too, then looked for them in experiments, and lo and behold found them (although physicists usually find whatever they're looking for). T

This relationship between the leptons and the quarks (thought to be fundamental particles), to me and others, suggests that perhaps there is an underlying fundamental particle or set of particles that leptons and quarks are constructed from. I am not well versed in quantum theory, perhaps it could be adapted to accomodate a new set of quanta?