A method to improve contrast in high resolution electron microscopy of ultrathin tissue sections

The general background granularity observed in out-of-focus electron micrographs is discussed as a phase contrast effect, that prevents higher resolution than about 25 Å on low contrast specimens as ultrathin tissue sections. The problem of improving the specimen resolution when dealing with ultrathin sections consists of improving the contrast so that in-focus pictures may be used. A method of mounting the sections on formvar nets is described, which makes it possible to obtain pictures of sections, which are partially not supported by a formvar film. The reduced diffuse scattering of the electrons when passing through these areas means a drastic increase of contrast.