As surprising as it may sound, no one really knows what an electron is, and it is this fundamental question that has been the driving force for much of modern physics and eventually led to the development of quantum field theory.
To answer the question “What is an electron?”, you would think the first step would be to observe it. However, that is easier said than done. Electrons are simply too small for us to observe – the smallest thing we can observe is an atom and even that is not observed with a traditional microscope. Read more..