This chapter presents the second strategy followed to optimize coherent electron microscopy methods, which consists in working directly on the source technology. Improving their intrinsic brightness or generating new properties while maximizing brightness are the two directions followed in our work. The chapter will describe the development of a new emitter based on a carbon nano-cone after introducing the technology of the brightest sources now encountered in electron optics, namely cold field emission guns (CFEG). We will then conclude with a description of the ultrafast CFEG currently used to develop new kind of coherent time-resolved microscopy methods.