This manual explains the basic principle, composition and operating method of a Transmission Electron Microscope (TEM), using visual materials for a better understanding. It is published to be used in using equipment by providing tips on how to use and manage the equipment. A TEM uses accelerated electrons as light source. Because electron negative charge, it is strongly diffracted in sensitive response to materials, compared to electromagnetic waves and x-ray. Therefore, it is good for observing images in local atomic arrangement and analyzing crystallography. Electron beam is used to observe structure in a micro area by easily focusing within several Å using a proper tool such as electromagnetic lens. A TEM is used in the micro-analysis of materials such as interactive response in thin film/substrate interface where change in crystal structure or elemental concentration gradient is steep. After conducting morphological, crystallographic, and chemical analyses throughout material sectors such as metal, semiconductor, polymer and ceramics, it is used in analyzing interface response, defect, and crystallinity, understanding phase change and determining the causes of the defect.