Cryo-electron microscopy of vitrified specimens was just emerging as a practical method when Richard Henderson proposed that we should teach an EMBO course on the new technique. The request seemed to come too early because at that moment the method looked more like a laboratory game than a useful tool. However, during the months which ellapsed before the start of the course, several of the major difficulties associated with electron microscopy of vitrified specimens found surprisingly elegant solutions or simply became non-existent. The course could therefore take place under favourable circumstances in the summer of 1983. It was repeated the following years and cryo-electron microscopy spread rapidly. Since that time, water, which was once the arch enemy of all electronmicroscopists, became what it always was in nature – an integral part of biological matter and a beautiful substance.

SUMMARY Thin layers of pure water or aqueous solutions are frozen in the vitreous state or with the water phase in the form of hexagonal or cubic crystals, either by using a spray‐freezing method or by spreading the liquid on alkylamine treated films. The specimens are observed in a conventional and in a scanning transmission electron microscope at temperatures down to 25 K. In general, the formation of crystals and segregation of solutes during freezing, devitrification and evaporation upon warming, take place as foreseen by previous X‐ray, thermal, optical and electron microscopical studies. Electron beam damage appears in three forms. The devitrification of vitreous ice. The slow loss of material for the specimen at a rate of about one molecule of pure water for every sixty electrons. The bubbling in solutions of organic material for doses in the range of thousands of e nm−2. We propose a possible model for the mechanism of beam damage in aqueous solutions. The structural and thermal properties of pure frozen water important for electron microscopy are summarized in an appendix.

The phase behavior of aqueous solutions of several dissymmetric gemini surfactants (with two hydrophobic chains of different lengths) was studied. From rheological and X-ray scattering studies as well as from freeze fracture imaging, some general patterns of the phase behavior were observed which are remarkably different from those observed for monomeric surfactants. The sequence of phases observed with increasing surfactant concentration was an isotropic wormlike micellar phase, multilayered structures which are first isotropic and then organized with orientational ordering, and an inverted hexagonal phase. The multilayered phase showed a scattering peak corresponding to a periodicity of 40 Å indicating the presence of stacks of bilayers without a water layer in between. For some of the samples, cryo-TEM showed that wormlike micelles (WLM) evolve into a ribbonlike structure (elongated bilayer). Upon further increase in concentration, the ribbons transform into multilayered structures with a well-defined width.