Abstract：The formation and evolution of galaxies in general and our Galaxy in particular, are often treated as separate problems in astrophysics. However, they are both part of the same fundamental question on how galaxies form and evolve in a cosmological context. The dramatically different physical scales between the traditional observations of the Milky Way and of external galaxies have so far hindered scientists from using both approaches simultaneously. This situation is now rapidly changing thanks to the great advancement in observations in both Milky Way and external galaxies. In this talk, I would like to introduce my past, ongoing and future planned researches on galaxy formation and evolution from the perspective of chemical evolution utilising the observations of both Milky Way and external galaxies and my chemical evolution model.