Galactic Stellar Populations
  The history of the formation and evolution of the Milky Way Galaxy is found in the spatial distribution, kinematics, age and chemical abundance distributions of long-lived stars. From this fossil record one can in principle extract the star formation histories of different components, their chemical evolution, the stellar Initial Mass Function, the merging history -- what merged and when did it merge? -- and compare with theoretical models. Observations are driving models, and we live in exciting times. 
Rosemary F.G. Wyse and Gerard Gilmore