One of the reasons for writing this story in its present form is to help the reader to realise that electrons are not mythical, but real existing things, and by far the most interesting things we know anything about. The discovery of electrons has shed a new light upon the meaning of very many things which have been puzzles until now. They give us a reasonable explanation of the cause of light and colour. They provide a new idea of the constitution of matter. They enable us to picture an electric current, and they give us definite, though by no means final, answers to the why and wherefore of magnetism, chemical union, and radio-activity.<br />The story is imaginary only in so far that one of the electrons itself is supposed to tell the tale. But in the endeavour to make the story interesting, there has been no sacrifice of accuracy in the statements of fact.