A method of shadowing samples directly within the electron microscope has been developed in this Laboratory. This method, which uses thallium chloride immersed in distilled water as the shadowing material, is much less time consuming than is the usual method that involves high‐vacuum metal evaporation; the results obtained are not of the same high quality as those of the usual method, but the time saving often justifies the method. Polystyrene Latex (batch No. 580) is introduced on the specimen screen, to provide an internal calibration standard; this standard makes it possible to measure the angle of shadowing.