Any compound requires its 3D atomic structure to become ultimately “fully characterized”. However, only 10% of all crystalline substances are described accordingly. The reason: Present diffraction methods are only applicable to samples of sub-millimeter sizes. ED overcomes this limitation and allows investigations on nano-crystalline systems, i.e. at least 1 million times smaller in volume. For example in drug discovery hundreds of thousands of known but not fully characterized crystalline compounds could be rapidly screened for their scientific or commercial potential. This applies also for many other fields, such as MOFs, zeolithes, minerals, and natural products.