Introduction / Jed Z. Buchwald and Andrew Warwick -- I, Corpuscles and electrons. J.J. Thomson and the electron, 1897-1899 / George E. Smith -- Corpuscles to electrons / Isobel Falconer -- The questionable matter of electricity: the reception of J.J. Thomson's "corpuscle" among electrical theorists and technologists / Graeme Gooday -- Paul Villad, J.J. Thomson, and the composition of cathode rays / Benoit Lelong -- II, What was the newborn electron good for? The Zeeman effect and the discovery of the electron / Theodore Arabatzis -- The electron, the protyle, and the unity of matter / Helge Kragh -- O.W. Richardson and the electron theory of matter, 1901-1916 / Ole Knudsen -- Electron gas theory of metals: free electrons in bulk matter / Walter Kaiser -- III, Electrons applied and appropriated. The electron and the nucleus / Laurie M. Brown -- The electron, the hole, and the transistor / Lillian Hoddeson and Michael Riordan -- Remodeling a classic: the electron in organic chemistry, 1900-1940 / Mary Jo Nye -- The physicists' electron and its appropriation by the chemists / Kostas Gavroglu -- Philosophical electrons. Who really discovered the electron? / Peter Achinstein -- History and metaphysics: on the reality of spin / Margaret Morrison -- What should philosophers of science learn from the history of the electron? / Jonathan Bain and John D. Norton -- The role of theory in the use of instruments; or, How much do we need to know about electrons to do science with an electron microscope? / Nicolas Rasmussen and Alan Chalmers.