An electron, the first elementary particle discovered, has no discernible size, and is considered to have none in principle. It’s not that it has ZERO size, understand, it’s just that size is not one of its properties.
A property of electrons is that the mass of the electron increases by a few orders of magnitude as it is super cooled. At or close to absolute zero while the mass has increased thousands of times the electrons super conduct. Weird critters.