A new technology has been developed to fabricate lanthanum hexaboride (LaB6) single-crystal nanowires with clean surface, a promising cold field-emission electron source for electron microscopes and other devices, and thereby improved the performance and stability of the electron source. Furthermore, by installing the new electron source into a scanning electron microscope, they successfully obtained high-resolution images, demonstrating that the electron source can actually serve as a source of ultra-bright electron beams for electron microscopes.