[Cryo-microscopy, an alternative to the X-ray crystallography?]. 
Recent technological advances have revolutionized the field of structural biologists.  Specifically, dramatic progress related to the development of new electron microscopes and image capture (direct electron detection camera) and the provision of new image analysis software has led to a breakthrough in terms of resolution attained using cryo-electron transmission microscopy.  It is thus possible to calculate relatively quickly high-resolution structures of biological molecules whom structural study still resists to more conventional methods such as X-ray diffraction or nuclear magnetic resonance (NMR).  These structures thus obtained may also bring complementary structural information to those already described by other methods.  Some of these new structures resolved through cryo-electron microscopy revealed for the first time the precise operation of essential mechanisms necessary for the good physiological process of a cell.  The ability to solve these structures at atomic resolution detail is essential for the development of new drugs that target these proteins of therapeutic interest.  Thanks to these advanced techniques that we summarize in this revew, biological and medical issues have now become accessible, whereas this approach was inconceivable only five yeras ago. ‡.