The development is briefly reviewed of the cathodes that have brought about epoch-making progresses in surface science and electron beam technology: the carbon filament by Edison(1884), the tungsten filament by Langmuir(1913), the LaB₆-cathode by Lafferty(1951) and the Zr-O/W(100) cathode by Swanson(1979). These developments stimulated the surface scientists in those days to devise atomic level characterization tools for elucidating such characteristics of the cathodes as high brightness, high stability and long service life. These approaches have led to many discoveries of practical importance; the water-vapor cycle on the tungsten surface (Langmuir), the double layer formation on the Cs/W(100)-surface (MacRae, et al.), the critical temperature for the stoichiometric evaporation in LaB₆-cathode (Aono, et al.) and the self-recovery function on the Zr-O/W(100) surface (Shimizu, et al.). [DOI: 10.1380/ejssnt.2003.106]