Nano ARPES is a class of spatially resolved ARPES that uses nano-focusing optics. A typical beam spot size is reached between 100 nm and 5um depending on optical design: Schwarzschild objectives, Fresnel zone-plate, and capillary mirrors are used for reaching submicron-sized beam. Whatever you choice the type of nano-focusing, a basic concept is started from the magnification ratio (or ratio of numerical aperture) which can be expect from the ratio between the length [from exit slit to nano focusing element] and [from nano focusing element and sample stage]. Nano ARPES, focusing a beam reaching sub-micron scale, open a future to explore the electronic structure in a tiny world: measuring the quasi-particles within a few-micron scale terminations, edge states, and devices.