Electron crystallography, although catching up fast, has a disadvantage: there is a strong interaction between the electrons of the probe and the sample itself. Now, T E Weirich and his colleagues have obtained the complete determination of an unknown structure for the compound Ti_11 Se_4 by electron crystallography. This is a landmark since the technique can now be used for determination of structure of crystals which are too small for X-ray diffraction and where powder diffraction is difficult ( Nature , Vol 382, No 6587).