In this paper, we present the theoretical background to electron scattering in an atomic potential and the differences between low-and high-energy electrons interacting with matter. We discuss several interferometric techniques that can be realized with low-and high-energy electrons and which can be applied to the imaging of non-crystalline samples and individual macromolecules, including in-line holography, point projection microscopy, off-axis holography, and coherent diffraction imaging. The advantages of using low-and high-energy electrons for particular experiments are examined, and experimental schemes for holography and coherent diffraction imaging are compared.