Nanoscience research is based on the development of new materials. The objective is to achieve new properties. The study of these properties requires the conservation of these new materials (in particular insulator and fragile) in their natural state during their observation and analysis. Obtaining and developing innovative materials needs the use of a suitable tool of characterization such as the variable pressure/environmental scanning and Transmission electron microscope (ESEM or ETEM).

Conventional Scanning and Transmission Electron Microscopy (CSEM and CTEM) equipped with a Microanalysis system are a convenient tool to analyze and to follow the structural evolution of the heterogeneous materials and working under high vacuum (about 10-5 Torr). In order to avoid sample preparation which introduces some artefacts and spent more energy this conventional technique is not suitable. Difficulty arises for insulating hydrated and biological materials. There is a much interest in introducing the gas environment in the specimen chamber which leads to the degradation of the high vacuum. The electron beam scattering by gaseous environment is the fundamental parameter limiting the performance of the Gaseous Scanning and Transmission Electron Microscopy (GSEM and GTEM). The beam skirt produced by the presence of the gas affects imagery and the microanalysis results by decreasing the resolution and different gases were used (water vapor, air, argon, nitrogen, helium….). Examples of application concerning materials, nanomaterials and environment are more encouraged.