Advantages of megavolt electron microscopy in biological research

New electron microscopes, operating within the megavolt range have opened important prospects for scientific research. These microscopes were, at first, mainly used by physicists and metallurgists; but nowadays more and more biologists are interested in high voltage electron microscopy: they have obtained important and significant results. The present paper gives more information concerning experiments that have been achieved in Toulouse with our two big instruments working at 1 million volts (1 MV) and three million volts (3 MV).