AbstractThe combination of energy dispersive X‐ray analysis with the transmission electron microscope enables the microscopist to rapidly identify features observed in the normal operation of the microscope, at high magnification. The development of equipment and techniques, especially in the art of specimen preparation, will now permit analysis of as little as 10‐18g, on a spatial scale of a few tens of nanometres. The importance of this technique in the biological and materials sciences promises to be as great as the contribution of the electron microscope its