Preon

A preon (litterally pre-quark) is the subcomponent of a quark, and a point particle. They are techincally hypothetical, but many paradoxes are resolved by requiring they exist. Attempts to find preons in our local Universe have been going on since 1974 AD. Each of the preon models postulates a set of preon particles smaller than those of the quark model.

Rishon
This was the oldest model of preon, divided into third rishons and vanishes rishons. The quark was assumed to be 3 rishons. The rishon model may explain the missing antimatter in our local Universe, as it may be locked up in rishons. But there are other preon theories also.