This book is aimed at the entire scientific community (solid state physics, chemistry, earth sciences, and live sciences), to those who use transmission electron microscopy (TEM) to analyze structure in relation to the properties and specific functions of materials. This work is essentially dedicated to the recommended methodology for beginning the preparation of a sample for the TEM. In particular it stresses the approach to take in selecting the best technique by taking into account the material problem presented, the type of material, its structure, and its properties. It proposes the tools for the most appropriate preparation of samples for observing the true structure of the material.