Cryo-Transmission Electron Microscopy is a method allowing visualisation of many of the delicate structures that form by self-assembly of amphiphilic molecules in aqueous environments. The amphiphiles may be surfactants, lipids, or polymers in alone or in various mixtures. The distinctive feature of the method is that the objects are examined without staining or dehydration. This is achieved by capturing the structures in very thin aqueous films that are subsequently vitrified and examined in the microscope at liquid nitrogen temperature. Objects in the size range from 5 to 500nm are well suited for the method. This includes various emulsion particles such as liposomes and more exotic cubosomes and hexasomes. In cryoTEM investigations perforated vesicles were found, an observation that triggered extensive studies of the nature and occurrence of such structures. As a complement to scattering methods, cryoTEM has proven its value in investigations of the size and morphology of various liposomal and vesicular systems. The microscopy studies show what type of structures that are present in the sample: uni- or multilamellar vesicles, open structures or closed defect-free vesicles, and if the form is spherical, tubular, or oblate, and so on. The scattering methods give good measures of size and polydispersity for defined systems.

In the lecture three main themes will be presented, where cryoTEM investigations provided decisive results and were the starting point for further studies:

• Morphology of cubosomes and other emulsion particles from dispersed liquid crystalline phases
• Perforated bilayer, there structure, nature, occurrence, and formation
• Spontaneous cationic vesicles: relationship to vesicles of zwitterionic lipids + ionic surfactants