The electron, discovered in 1897, was found to be a constituent of all atoms. While the nucleus of the atom remains fixed, the electrons are free to move with different amounts of energy. When supplied with more energy, by physical or mechanical means, light is produced when the original energy state is reached. Electrons can easily be removed altogether from the atom as in the case of electric current. This has given rise to our electrical and electronic industries. The associated magnetic field allowed motors and dynamos to be developed. Rapid movement of electrons results in the production of electromagnetic waves, from the longest wavelengths (radio waves) to the shortest wavelengths (gamma rays). This has had a huge impact on our lives in the fields of medicine and telecommunications. A beam of electrons can be directed in the same way as a beam of light. As light can show wave/particle duality so can an electron beam. Its measured wavelength is about the same as X-rays. This means electrons can be diffracted. The famous 'double-slit' experiment where a single electron appears to 'interfere with itself' cannot be explained by classical physics and so we enter the strange world of quantum mechanics. The birth of the quantum computer is not far away and will be much faster than existing computers. Finally, all chemical reactions are the result of electron movement between reactants.