What are electrons made of?

Question

Electrons have mass (9.11E-31 kg), which makes me wonder: what are they made?

Answer 1

As best we can tell, the electron is a fundamental particle, not a composite that is made out of anything.

An electron is a kind of lepton.  It is not made up of leptons.

The mass, like all masses, is a kind of energy.  What exactly that energy is, however, is not at all clear.  If you assume the electron is a point charge, it has infinite electrostatic energy.  But somehow that infinite energy gets canceled, and the remainder is the mass we measure.  It's possible that the masses of the fundamental particles are due to their interaction with the Higgs field.  If we discover a resonance in this Higgs field (a Higgs boson), we may be able to test how it interacts with other particles and see if such a coupling could be responsible for their masses.

Answer 2

leptons