Hi friends.
This is the most basic and simple question that striked me when i was studying electrostatics.
Here it is.

What is the composition of electron??
OR
Of which matter is electron made of??

The electron presently is considered as a fundamental particle, and has no further substructure. It actually belongs to a class of fundamental particles called leptons, which can't be broken down further.

Also you shouldn't view the electron as some kind of solid, spherical body. The electron is actually just considered as a point charge, which doesn't really have spatial existence. When we consider the effects of a number of electrons, they will be considered as a charge density, and it can be visualized as a cloud of charge, whose shape is determined by the probability of finding the electron at different points.

The electron by itself doesn't have any definite structure.