This lecture introduces transmission electron microscopy (TEM) and electron diffraction, covering topics such as TEM components, operation, imaging modes, diffraction analysis, and the resolving power of microscopes. It explores the history of electron microscopy, types of electron microscopes, signals in TEM, and the interaction of high-energy electrons with matter. The lecture also discusses the contrast mechanisms in TEM, high-resolution TEM, and the versatility of electron microscopy as a powerful tool for material science.