Bose-Einstein Condensation (BEC) in dilute atomic gases has extensively been studied both experimentally and theoretically. Its principle is to be mentioned, as well as important techniques to realize BEC, such as those for laser cooling and evaporative cooling. As an example of new BEC studies, BEC in a system with a spin degree of freedom is also mentioned, for which we propose here an application of optical magnetic resonance imaging (MRI) to observe the distribution of spin-polarized atoms with high resolution.