[en] X-ray diffraction is used to determine the structure of materials but with the development of nano metric materials or complex crystals, this technology is approaching its natural limits. Transmission electronic microscopy (TEM) might have been the right tool to complete X-ray diffraction but the approximation implying that the particle is diffracted only once by the crystal is no valid for an electron while it is for an X-ray photon and as a consequence the relationship between the intensity of the diffracted electron beam and the structure factor of the crystal is complex and difficult to interpret. A new kind of TEM named precession electronic diffraction (PED) reduces the issue linked to multiple diffractions. This technique consists in tilting the incident electron beam slightly and making it rotating around the optical axis. The obtained diffraction pattern is limited to a ring, which involves less reflexions and reduces the risk of multiple diffractions. (A.C.)