Abstract

The concept of J.J. Thomson’s classical point electron has proved good enough for most of magnetic lens-based electron optics including the recent revolution in aberration correction. The wave nature of the electron, discovered by G.P. Thomson as well as Davisson and Germer, was employed in other advances in electron microscopy such as diffraction contrast and structure imaging, electron holography and the revolutionary introduction of the field emission tunnelling tip. By comparison, we have found it much harder to harness the spin of Dirac’s electron for electron imaging. Even more remote from the electron microscopist’s tool box is the concept of Feynman’s electron interacting only through the creation and annihilation of virtual photons. Nevertheless, progressing through scanning electron microscopy with the cathodolumenescence signal, in photo-emission electron microscopy, in tip-enhanced near field microscopy and in super-resolution fluorophore optical imaging, the role of the photon in transforming many branches of microscopy is exploding. This situation will be reviewed and the prospects for optical pump probe electron microscopy will be discussed.