Transmission Electron Microscopy (TEM) has the capability to characterize the materials in its atomic structure. Image, diffraction, and spectroscopy can be used to obtain different information such as structure, chemical information, electronic structure, and magnetic information from nano-objects and bulk materials. All information acquired by TEM can be quantitative with accurate processing, which allows measuring the shape, size, size distribution, size homogeneity, lattice type, chemical composition, binding energy among other information. Moreover, in situ microscopy opens up to observe and quantify structure, chemical and phase transformation on the timescale. In this way, TEM can be classified as an important tool for studying and researching in nanoscience and nanotechnology.